Thanks Shooty. - PS it was your thread where the linear control using micro switches was listed.

I have a bit of titanium plate behind rear bulkhead coring out some holes here would-be low risk
Once I know exactly where the internal electronics will be located I can drill the holes in the floor.
The aluminium square is 2mm so a few holes is not going to weaken it considerably

I am thinking of using polycarbonate with a thin Ti sheet on top for the bottom of the ramp. A composite structure you could say. It could take big whack and be lighter than steel I think. Anybody tried something similar?