I would not mess with that kind of stuff (adding 1.5 inches). It will probably only give you headaches in the end. If headroom seems to be such a big problem, you should get a high quality foam and take the 1.5 inches off the seat foam, thus giving you the added 1.5 inches. I've had people as big as 6'5" and they fit okay. My foam is pretty thick, but it compresses pretty well. Andy Judge