Upholstering foam driver seat recommendations?

Alright so I recently hurt my back (3 lower lumbar slipped discs) and now the seat hurts. I am 6'2" -3" inseam of 38-40. I want to add foam to the rear of the seat and kind of flatten the seat bolsters. just want to know how other people have measured their Addition of foam or how have you achieved a nice seat. I have added spacers to the seat, but no luck. I currently sit on 3 inch memory foam and gel infused padding on top. don’t worry if you can’t help, the upholstery shop told me they will redo it one time after if it doesn’t work. So most likely I will just have to test and tune it.

 

On my old truck I bought a thick, CoverCraft seat cover and tried putting different pieces of foam and small pillows under the cover in different places/orientations until I felt comfortable......