OK, so now we're getting somewhere! Although there's no way of knowing whether or not my particular A1200 would require a timing fix, for some reason still unknown to me, a 1990's accelerator wouldn't require this fix.
Apart from that, if I can find a copy of "3D Master", and if I'm happy with a resolution of 320x400 original HAM mode, then although I doubt I can still register it, this might be able to render one frame overnight in about 10 hours, because your 320x400 HAM pics took 20 hours.
Not all 1990 accelerators are safe either. If you want to be sure then your only real bet is one of the blizzard accelerators. These had a buffered interface, I believe, which means that any timing issues would be taken care of by the card. The Apollo's and these new accelerators do not have this, which makes them faster but less stable