It can be done, you have to find a pin compatible flash chip that can be put in the bios chip's place. That's how the CD Unibios was installed into my CDZ. I'm afraid I can't give specifics since I didn't do the work.
I think you are refering to this thread that I created:
http://www.neo-geo.com/forums/showthread.php?277528-AM29F400BT-as-bios-replacement-MV1C
I woudn't bother, just use a Neo Bios Masta. If it's not disponible in his site you can order it from OSH park or download the gerber and order in another site.
Just don't sell it like an asshole from my country did.
can you open your neogeo cd and take a picture of the bios area, please?