I hope I've done the right thing!
But this morning I got up, dragged the Phantom out, stared at it for quite some time, then proceeded to strip it and take angle grinder to the frame!
I was going to have to sell it otherwise!
This is a sweet little motor, that it seemed a shame to have to detune for the angle fire head, and a good strong, compact and steel frame. However it rides a little rough on the 24" wheel chair tyres and didn't have room in the frame for anything wider.
Pedal is a little close to the front tyre, but I don't plan to need much pedal power.
The mock up, looks to give good wheel base, good rake, good ground clearance for the crank arms, just enough room to fit a center fire head with a tidy, compact, strong and reasonable weight frame.
This looks like it!