diff --git a/src/main/CMakeLists.txt b/src/main/CMakeLists.txt
index da19602209d..e8bc3faba65 100755
--- a/src/main/CMakeLists.txt
+++ b/src/main/CMakeLists.txt
@@ -415,6 +415,8 @@ main_sources(COMMON_SRC
     mavlink/mavlink_mission.c
     mavlink/mavlink_mission.h
     mavlink/mavlink_modes.c
+    mavlink/mavlink_msg_entry.c
+    mavlink/mavlink_msg_entry.h
     mavlink/mavlink_modes.h
     mavlink/mavlink_types.h
     mavlink/mavlink_ports.c
diff --git a/src/main/fc/fc_mavlink.c b/src/main/fc/fc_mavlink.c
index 02bdfb84fc4..1205438c5cc 100644
--- a/src/main/fc/fc_mavlink.c
+++ b/src/main/fc/fc_mavlink.c
@@ -419,6 +419,7 @@ mavlinkFcDispatchResult_e mavlinkFcDispatchIncomingMessage(uint8_t ingressPortIn
         return mavlinkHandleIncomingTimesync() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
     case MAVLINK_MSG_ID_PARAM_REQUEST_LIST:
         return handleIncoming_PARAM_REQUEST_LIST() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
+#ifndef USE_TELEMETRY_MAVLINK_CONSTRAINED
     case MAVLINK_MSG_ID_MISSION_CLEAR_ALL:
         return mavlinkHandleIncomingMissionClearAll() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
     case MAVLINK_MSG_ID_MISSION_COUNT:
@@ -429,16 +430,19 @@ mavlinkFcDispatchResult_e mavlinkFcDispatchIncomingMessage(uint8_t ingressPortIn
         return mavlinkHandleIncomingMissionItemInt() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
     case MAVLINK_MSG_ID_MISSION_REQUEST_LIST:
         return mavlinkHandleIncomingMissionRequestList() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
+#endif
     case MAVLINK_MSG_ID_COMMAND_LONG:
         return mavlinkHandleIncomingCommandLong() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
     case MAVLINK_MSG_ID_COMMAND_INT:
         return mavlinkHandleIncomingCommandInt() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
+#ifndef USE_TELEMETRY_MAVLINK_CONSTRAINED
     case MAVLINK_MSG_ID_MISSION_REQUEST:
         return mavlinkHandleIncomingMissionRequest() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
     case MAVLINK_MSG_ID_MISSION_REQUEST_INT:
         return mavlinkHandleIncomingMissionRequestInt() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
     case MAVLINK_MSG_ID_MISSION_ACK:
         return mavlinkHandleIncomingMissionAck() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
+#endif
     case MAVLINK_MSG_ID_REQUEST_DATA_STREAM:
         return mavlinkHandleIncomingRequestDataStream() ? MAVLINK_FC_DISPATCH_HANDLED_ACTIVITY : MAVLINK_FC_DISPATCH_NOT_HANDLED;
     case MAVLINK_MSG_ID_RC_CHANNELS_OVERRIDE:
diff --git a/src/main/mavlink/mavlink_mission.c b/src/main/mavlink/mavlink_mission.c
index 08141b4f086..abd959ad597 100644
--- a/src/main/mavlink/mavlink_mission.c
+++ b/src/main/mavlink/mavlink_mission.c
@@ -4,7 +4,7 @@
 #include "mavlink/mavlink_mission.h"
 #include "mavlink/mavlink_runtime.h"
 
-#if defined(USE_TELEMETRY) && defined(USE_TELEMETRY_MAVLINK)
+#if defined(USE_TELEMETRY) && defined(USE_TELEMETRY_MAVLINK) && !defined(USE_TELEMETRY_MAVLINK_CONSTRAINED)
 
 /*
  * Mission transfer retry and partner tracking are adapted from Betaflight's
diff --git a/src/main/mavlink/mavlink_msg_entry.c b/src/main/mavlink/mavlink_msg_entry.c
new file mode 100644
index 00000000000..f0f972b9498
--- /dev/null
+++ b/src/main/mavlink/mavlink_msg_entry.c
@@ -0,0 +1,30 @@
+/*
+ * This file is part of INAV.
+ *
+ * INAV is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * INAV is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with INAV.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "mavlink/mavlink_types.h"
+
+#if defined(USE_TELEMETRY_MAVLINK) || defined(USE_SERIALRX_MAVLINK)
+
+/*
+ * The single instantiation of the MAVLink helpers for the whole firmware.
+ * MAVLINK_SEPARATE_HELPERS (see mavlink_msg_entry.h) leaves MAVLINK_HELPER
+ * empty and stops protocol.h including these, so this is the only place they
+ * are defined, with external linkage.
+ */
+#include "mavlink_helpers.h"
+
+#endif
diff --git a/src/main/mavlink/mavlink_msg_entry.h b/src/main/mavlink/mavlink_msg_entry.h
new file mode 100644
index 00000000000..6f66fd8c3b0
--- /dev/null
+++ b/src/main/mavlink/mavlink_msg_entry.h
@@ -0,0 +1,36 @@
+/*
+ * This file is part of INAV.
+ *
+ * INAV is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * INAV is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with INAV.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+/*
+ * protocol.h compiles the MAVLink helpers as MAVLINK_HELPER = static and
+ * includes them into every translation unit, so each one gets a private copy of
+ * every helper it touches - and of the static data inside them. Nothing warns
+ * about it: the copies are static data rather than unused code, so no
+ * diagnostic fires and nothing shows up in a diff.
+ *
+ * The message table is the expensive case. mavlink_get_msg_entry() holds it as
+ * a function-local static, and two callers - routing and runtime - meant two
+ * copies of a 4044 byte table.
+ *
+ * MAVLINK_SEPARATE_HELPERS is the library's own switch for this: protocol.h
+ * then emits declarations only, and mavlink_msg_entry.c compiles the helpers
+ * once with external linkage. This header must be included before
+ * storm32/mavlink.h so the switch is set before protocol.h is reached.
+ */
+#define MAVLINK_SEPARATE_HELPERS
diff --git a/src/main/mavlink/mavlink_runtime.c b/src/main/mavlink/mavlink_runtime.c
index 6fce0de2422..fb477bb0ca8 100644
--- a/src/main/mavlink/mavlink_runtime.c
+++ b/src/main/mavlink/mavlink_runtime.c
@@ -279,8 +279,10 @@ static bool isMAVLinkTelemetryHalfDuplex(uint8_t portIndex)
 
 void mavlinkRuntimeHandle(timeUs_t currentTimeUs)
 {
+#ifndef USE_TELEMETRY_MAVLINK_CONSTRAINED
     mavlinkSendPendingMissionItemReached();
     mavlinkMissionUpdate(currentTimeUs / 1000);
+#endif
     mavlinkSendModeStatusText();
     mavlinkSendArmingStatusText();
 
diff --git a/src/main/mavlink/mavlink_types.h b/src/main/mavlink/mavlink_types.h
index 8fb2f9e6b7e..1d1476fd732 100644
--- a/src/main/mavlink/mavlink_types.h
+++ b/src/main/mavlink/mavlink_types.h
@@ -28,6 +28,7 @@
 #ifndef MAVLINK_COMM_NUM_BUFFERS
 #define MAVLINK_COMM_NUM_BUFFERS MAX_MAVLINK_PORTS
 #endif
+#include "mavlink/mavlink_msg_entry.h"
 #include "storm32/mavlink.h"
 #pragma GCC diagnostic pop
 
diff --git a/src/main/rx/mavlink.h b/src/main/rx/mavlink.h
index 0290b010003..7396825cac7 100644
--- a/src/main/rx/mavlink.h
+++ b/src/main/rx/mavlink.h
@@ -22,6 +22,7 @@
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wunused-function"
 #define MAVLINK_COMM_NUM_BUFFERS MAX_MAVLINK_PORTS
+#include "mavlink/mavlink_msg_entry.h"
 #include "storm32/mavlink.h"
 #pragma GCC diagnostic pop
 
diff --git a/src/main/target/common.h b/src/main/target/common.h
index d339e6620ae..3c997b74d02 100644
--- a/src/main/target/common.h
+++ b/src/main/target/common.h
@@ -424,9 +424,16 @@
 #endif
 
 //Designed to free space of F722 and F411 MCUs
-#if (MCU_FLASH_SIZE > 512)
-#define USE_TELEMETRY_MAVLINK
 #define USE_SERIALRX_MAVLINK
+#if (MCU_FLASH_SIZE > 512)
+    #define USE_TELEMETRY_MAVLINK
+#endif
+
+#if defined(MCU_FLASH_SIZE) && (MCU_FLASH_SIZE <= 512)
+    #define USE_TELEMETRY_MAVLINK_CONSTRAINED
+#endif
+
+#if (MCU_FLASH_SIZE > 512)
 #define USE_TELEMETRY_SIM
 #define USE_VTX_FFPV
 #define USE_SERIALRX_SUMD
diff --git a/src/main/target/common_post.h b/src/main/target/common_post.h
index a27835731cc..a6e3ed2a440 100644
--- a/src/main/target/common_post.h
+++ b/src/main/target/common_post.h
@@ -19,6 +19,13 @@
 
 #pragma once
 
+// Constrained MAVLink, selected by flash size in common.h: the full subsystem
+// minus MAVLink mission transfer, which does not fit on a 512 KB target.
+// Missions themselves are unaffected - they are managed over MSP.
+#ifdef USE_TELEMETRY_MAVLINK_CONSTRAINED
+#define USE_TELEMETRY_MAVLINK
+#endif
+
 // MSP-over-MAVLink is independently removable from MAVLink targets that cannot
 // afford its reply buffer. Define DISABLE_MAVLINK_MSP_TUNNEL in a target to
 // retain normal MAVLink without the tunnel RAM/code cost.
diff --git a/src/test/unit/CMakeLists.txt b/src/test/unit/CMakeLists.txt
index ce7813f033d..44cae96d829 100644
--- a/src/test/unit/CMakeLists.txt
+++ b/src/test/unit/CMakeLists.txt
@@ -80,7 +80,7 @@ set_property(SOURCE gimbal_serial_unittest.cc PROPERTY definitions USE_SERIAL_GI
 
 set_property(SOURCE mavlink_unittest.cc PROPERTY depends
     "fc/fc_mavlink.c" "mavlink/mavlink_command.c" "mavlink/mavlink_guided.c" "mavlink/mavlink_mission.c" "mavlink/mavlink_modes.c" "mavlink/mavlink_ports.c"
-    "mavlink/mavlink_routing.c" "mavlink/mavlink_runtime.c" "mavlink/mavlink_streams.c" "telemetry/mavlink.c"
+    "mavlink/mavlink_msg_entry.c" "mavlink/mavlink_routing.c" "mavlink/mavlink_runtime.c" "mavlink/mavlink_streams.c" "telemetry/mavlink.c"
     "common/crc.c" "common/maths.c" "common/streambuf.c" "common/string_light.c" "msp/msp_serial.c")
 set_property(SOURCE mavlink_unittest.cc PROPERTY definitions USE_TELEMETRY USE_TELEMETRY_MAVLINK USE_MAVLINK_MSP_TUNNEL)
 set_property(SOURCE mavlink_unittest.cc PROPERTY extra_includes