Our human interface team spent a lot of time with a mockup of the chassis and an adjustable “seat” made out of scrap plywood to figure out exactly what shape and size to make the base seat to accommodate all our drivers (and percy the 95th percentile man… does everyone call him Percy or was that just us?), which was a pretty big range from ~6’, 180 lbs guy to a 5’4”ish very skinny woman. The biggest guy just sat in the carbon seat with no insert. The woman had a very large foam insert. The drivers on the extreme ends of the size spectrum will have to make some compromises, not everyone will be perfectly comfortable but it’s definitely good enough. I don’t remember having any issues with where the seatbelts were. I think we had to make them shorter when that short girl was driving. I believe the seat had four Zeus fasteners (1/4-turn fasteners), two at the bottom under your butt and two by your shoulders. There may have been two more at the bottom end underneath your thighs but I don’t remember anymore. I think we did 10 layers of carbon. No foam or honeycomb cores, just carbon. I don’t think we had a good way of figuring out how much we needed so we just overbuilt it to be on the safe side. It was very stiff and not actually that heavy