Dimensions....................
Length is 2 feet or 610mm.
Minimum width is 20mm. This is not critical. The metal runners are 20mm wide so 20mm spacers are very tidy. I'm using slightly wider spacers for the new car.
The hole for the protruding nut needs to be 15mm or 16mm.
The holes for the fixing bolts can be 10mm if you can achieve perfect alignment, but 13mm holes will allow some wriggle room.
Hole centres from the front are 13mm; 96mm; 185mm for the nut hole; 508mm.
Height? I'm now using 10mm thickness. You can use up to 30mm but at that there is not much thigh space under the steering wheel.
In my Roadster with factory wood, and the higher dash, the spacers are 30mm at the front and about 20mm at the rear - so a front to rear taper. Minor adjustments can be made with washers and as noted above, you can just use washers under the runners on each fastener to lift the protruding nut off the floor.
Longer bolts may be necessary.
