These are larger than most Bomber seats. I'd do them pretty much exactly like you said. The sides will have to be very thin, at least on the inside, or you won't have much seating area left, I would sew the outside back, outside sides and inside sides all together using French seams, put that all on first, and then velcro in the seat bottom pad and the seat back pad. The seat bottom and lower seat back would be rectangles, and the upper seat would flare out on both sides and top.
The bolts are for some type of restraint system?
No one lives forever, the trick is creating something that will.