This is what I plan to model my seats on (without the rear hydraulics!).
This will be a project for those dark evenings from December to February.
They will be a ply/aluminium mix, with my leather being used to cover pad inserts. I will make the base fit wherever it has to, and will keep it as shallow as possible.
The seat bases on the MkI Spitfires were made from a paper/resin mix. Not sure they would have passed an SVA test.
I may even include the flare holders along the front. I should be able to fit a small can of coke in them.