Not that this helps, but the author of the rcs xcalibur actually sold his a4000 a couple years ago on Canada ebay. Unfortunately i didnt have the money to buy it but i did email him and he told me the 4000 had the designs for the xcalibur on it sold along with Proboard amiga pcb software(which he claimed proboard author made a special gfx card compat. version for him) it was designed with. I tried to get him to release the designs,but he wouldn't.
I don't know who ended up with the A4000 but sadly its probably in someones closet.