rcS file in PX4 F/W

I’m trying to upload the PX4 F/W on STM32F446 instead of STM32F427 (Pixhawk & PixRacer).

STM32F446 has small flash size (512KB), so I’m trying to reduce F/W size.

Firstly, I deleted some components in cmake file. After that, I’m trying to revise rcS file. (Firmware/ROMFS/px4fmu_common/init.d/rcS)

I can understand the source code in this file approximatively, but if there is a manual, document or website, it will be very helpful to me.

Please let me know any information about this.

Removing all the mixers and airframes you aren’t going to use will help.
Did you strip the cmake config down to the bare minimum?

Yes, the F/W size is about 490 KB now.
So, I think there are many parts that need to be deleted in rcS source code.