I'm trying to do this now with no success. There are 2 versions of the bios contained in the RAR from "the usual places". One version is for 1.0-1.5 xboxes, the second is for 1.6 + 1.6b boxes. The "old" version opens nicely in XBtool and I can make a BFM from that. Not much good for me though (at least not on this xbox, my other 2 are older models).
Has anybody had any success making a BFM version of the X2 5035 bios that will run on the 1.6 boxes?