diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
index 21871dd9ec..0754bcfdd0 100755
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
@@ -828,6 +828,7 @@ def build_peripheral_list():
 
 def process_line(line):
     '''process one line of pin definition file'''
+    global allpins
     a = shlex.split(line)
     # keep all config lines for later use
     alllines.append(line)
@@ -864,11 +865,24 @@ def process_line(line):
     if a[0] == 'SPIDEV':
         spidev.append(a[1:])
     if a[0] == 'undef':
+        print("Removing %s" % a[1])
         config.pop(a[1], '')
+        bytype.pop(a[1],'')
+        bylabel.pop(a[1],'')
         #also remove all occurences of defines in previous lines if any
-        for line in alllines:
+        for line in alllines[:]:
             if line.startswith('define') and a[1] in line:
                 alllines.remove(line)
+        newpins = []
+        for pin in allpins:
+            if pin.type == a[1]:
+                continue
+            if pin.label == a[1]:
+                continue
+            if pin.portpin == a[1]:
+                continue
+            newpins.append(pin)
+        allpins = newpins
 
 
 def process_file(filename):
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/skyviper-v2450/hwdef.dat b/libraries/AP_HAL_ChibiOS/hwdef/skyviper-v2450/hwdef.dat
index eaee46d22c..093a3a156a 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/skyviper-v2450/hwdef.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/skyviper-v2450/hwdef.dat
@@ -4,24 +4,35 @@
 # start with fmuv3 base port
 include ../fmuv3/hwdef.dat
 
+# remove some unnecessary features from fmuv3
+undef UART8
+undef UART8_TX
+undef UART8_RX
+undef USART3
+undef USART3_TX
+undef USART3_RX
+undef HAL_WITH_UAVCAN
+undef IOMCU_UART
+undef AP_FEATURE_SBUS_OUT
+undef HAL_OS_FATFS_IO
+undef AP_FEATURE_RTSCTS
+undef HAL_WITH_RAMTRON
+undef IOMCU_UART
+
+UART_ORDER OTG1 UART4 USART2
+
 # enable AP_Radio support
 define HAL_RCINPUT_WITH_AP_RADIO 1
 
 define HAL_GPIO_RADIO_RESET      1 // PB0 GPIO from FMU3
 define HAL_GPIO_RADIO_IRQ       15 // PD15
 
-# disable FRAM for storage
-undef HAL_WITH_RAMTRON
-
 # setup defines for ArduCopter config
 define TOY_MODE_ENABLED ENABLED
 define ARMING_DELAY_SEC 0
 define LAND_START_ALT 700
 define LAND_DETECTOR_ACCEL_MAX 2.0f
 
-# disable IOMCU
-undef IOMCU_UART
-
 # support cypress and cc2500 radios
 SPIDEV cypress    SPI2 DEVID11 FRAM_CS     MODE0  2*MHZ  2*MHZ
 SPIDEV cc2500     SPI2 DEVID12 FRAM_CS     MODE0  4*MHZ  4*MHZ