So I finally got around to installing this and I've managed to get 800x600 working great. Took fiddling with the picasso96 modes until my monitor liked it.
Still can't get 320x400 or 640x480, would like to use 640x480 if I could.
Speed is good and it's very smooth at 800x600 using an AC500+AC1231, I do get what looks like artifacts in the form of small pixels on the screen here and there, so not sure what that is about.
Switches nicely between WHDLoad games and workbench, better than my A1200. Although pacmania now no longer works but other games I play don't appear to have an issue.
Of course Doom is very playable using indi ECS mode so that's also plus.
On to fixing the pixels and trying to get it to work at 640x480.