Here are some better images of the seat runners made from 50x100x3mm RHS. Not sure if these open channels will need strengthening but it is 3mm steel bolted to a steel seat and a steel floor through 4mm plate so probably not.
Zip ties hold the seat down in position after defoaming the base for a lower sitting position.
Well that's the steering wheel positioned, and for my next trick...
It's hanging from various parts of the garage by weld wire! The things you find yourself doing late at night!
