Out of curiosity I gave the demo a try, it's totally playable at 640x480 with an A2K/PIV/060. BUT - at least here, the CV3D was a lot slower than the PIV in Z2 mode for some reason... up to 1.5 MB/s as far as raw bus transfer (measured with bustest and cgxbenchmark).
I think A2000 compatibility was included on the CV64/3D as more of a marketing ploy than anything else. The ScanDoubler didn't work with OCS/ECS, and the card just didn't perform well. Only the PIV had a jumper to scale back to 2 MB bus allocation, so to not interfere with the 8 MB ZorroII RAM limit. In general, the CV64/3D was not great on Zorro2, and a lot of people don't seem to realize that. Glad you do!
- t