Hmmm i see this in the MAME video src file for black tiger
#define BGRAM_BANK_SIZE 0x1000
#define BGRAM_BANKS 4
i only count 3 in FBA
INT32 nBank = (bank & 3) * 0x1000;
ZetMapArea(0xc000, 0xcfff, 0, DrvBgRAM + nBank);
ZetMapArea(0xc000, 0xcfff, 1, DrvBgRAM + nBank);
ZetMapArea(0xc000, 0xcfff, 2, DrvBgRAM + nBank);
so i added a forth
INT32 nBank = (bank & 3) * 0x1000;
ZetMapArea(0xc000, 0xcfff, 0, DrvBgRAM + nBank);
ZetMapArea(0xc000, 0xcfff, 1, DrvBgRAM + nBank);
ZetMapArea(0xc000, 0xcfff, 2, DrvBgRAM + nBank);
ZetMapArea(0xc000, 0xcfff, 3, DrvBgRAM + nBank);
then made DrvBgRAM = Next; Next += 0x008000;
i can now get to level 3 in FBL without the game crashing but the background is missing some progress i guess LOL