All built and ready to try out. With a few extra blue lock nuts added for extra speed.

Used the 511 body as I had a spare one. it fits well, with pretty much the same cut out lines on the rear as the 511, and leaving a little bit extra on the front, and bending a bit of the material to cover the diff a bit better.
Also used the full under tray rather than the side pod type design, again with a little effort this fits well too.
Found it easier to fit the electrics than the 511, but really wish they would move the slipper nut and spring to the other side!
Also decided to use the alu caster blocks and rear hubs.