So, UNROM is the name of the board, not necessarily their components.
They just follow the same working principles as UNROM, and may change the fixed bank as done on Crazy Climber.
If I've done right the math, adding a latch to all 8 CPU bits would allow up to 4 Megabytes of ROM!! WOW!! And even more can be done if we also latch PPU bits!!
I confess that when I read 74161 mapper I thought it would use the same mapper as Battletoads. I think it's one of the simplest mappers ever done.
So, back on topic: I have flashed the game and put on my testboard. Excellent!! Looks and plays very smooth!! Congratulations Bisqwit for your excellent work!!
When I tested on the emulator, I had the option to save. Is the mapper 2 save feature I've suggested already implemented? Looks like I'll have to try adding a PRG RAM and see if it works.
Many thanks guys!! You're Great!!
Edit: corrected the math, should be 4 megabytes instead of 8.