ok. camera boot's from CF if the flags are : -1,*,-1 or 0,0,-1. Flags are F8000004, 8 and C. The names and things are like in the 400D. I think you have to check what are the flags while .fir - It's easy to change them as I wrote:
FFFF69A4 loadFlags
FFFF6990 writeFlags
They load and save an aray of bytes. Copy them first to RAM like in
FFFF0E30 RunTheLoader
NEW: Ah, I forgot: the flags in 400D are -1 -1 -1 when booting.