I like what Mike did in Rich's car....I think it would work nicely for you since you don't seem to be as concerned with the extra rigidity that a 4-point roll bar will give you. This will allow for a removable harness bar for open track days, auto-x, ect. with the safety for rear seat passengers on the other days. And DO NOT just bolt harnesses to the floor!
You can see pics of this harness bar install in the first 31 pages of
this folder.
