Quote from Dwedit
"Flubba's trick for PocketNES to simulate Punch Out was deemed to be "bad" and "hacky" by Loopy, so it was never integrated into NesDS.
Punch Out works by the tilemap containing specific tile numbers that tell the mapper to bankswitch to a second set of vrom pages, and can also tell it to switch back to the first set of graphics again.
I think there may be a proper way to do punch out.
Use the GBA windowing feature to split the screen horizontally. Then use an additional background layer. This lets you have up to two vrom switch events per scanline. It would fix Punch Out and Marble Madness, and also probably the mapper 10 games, like fire emblem and famicom wars.
It would take a fair amount of work to add it in though."
I will see what i can do with two mirrors set up for each tile map and hopefully this will fix everything wrong with Punch Out and Marble Maddness etc. (Map 9,10)