The memory address space for the CPU slot on the A3000(T)/A4000(T) is limited to 128MB max anyway. This means 256MB is impossible unless GVP devised some way to get around this limitation (which I doubt). I'm guessing that's why the RAM board has 6 slots (plus 2 on the T-Rex) to accomodate 8x16MB GVP SIMMs for 128MB.
I wish I had one of these when I owned a T-Rex board. Reason I sold mine was because it could not take any more RAM than the 32MB it had on it.
