Get A Word of Advice at INPursuit.
By the way how did you make your actual cartridge edge? Just wondering for when I'm prototyping my design before I make a PCB for it.
Also I've determined all the information needed for battery saved games on the Genesis of any size now. Turns out it uses the previously unknown pin B31. I need to write up a better document though than the one I have currently.
Though your SNES Hi-ROM mapper is interesting since I was unsure how that works. I hope you don't mind if I use your design for the basis of mine.