Both Compactflash.device and FAT95 support TD64 which basically means that cards can go well over 1 TB, so I doubt the 4GB size is the problem.
You can try to edit the CF0 mountfile and change this (got it from the compactflash.device doc):
Damaged or simply not quite officially standardized cards may sometimes
cooperate using
Flags = 2 /* skip invalid PCMCIA signature */