I agree with RideBurton164, I always flash with a 1024k Bios, that way I know the first 512k will be on Bank1 and the Second 512k on Bank2.
I do the following:
1) Launch X2 Bios Manager Version 2.3,.
2) Right click Bank1 and Open a Copy of FlashBios (either 3.0.1 or 3.0.3)
3) Repeat step 2 for Bank 2
4) Right click Bank3 and Open a Copy of m8_16 (what ever variant you are using)
5) Repeat Step 4 for Bank 4
6) Left click Bank1, hold shift and Left click Bank4 (this will select all banks)
7) From "Selected Bank Options" , click Save. Give it a name of Bios.bin
You have just created a 1Meg Bios image with Flashbios on the First Bank and m8_16 on the second.
Burn the newly created Bios.bin to a CDRW along with a 100Mb Dummy file as per the Cromwell flashing tutorial and you should be able to Flash your chip now.
I always keep a version of Cromwell on the Chip, but I assume the same technique can be used to flash via Evox (although I have never done this).
This wont be everyone's method of choice, but I have never had this fail yet ... Touch wood.