I wouldn't attach the shoulder portion to the floor, because in a crash it could cause spinal compression = not good. They should come up over the shoulder and relatively straight back to an attachment point.
They should, but that is the problem when there is no solid place to attach them.
I have four point cam release belts with high back buckets, but still not comfortable about the shoulder belts unless they are attached to a bar at that height and not the seat floor brackets.
I still have the original lap belts also, and the lap section of the four point belts is mounted at the same points as the originals are.
Being a hard top car doesn't make it any easier, due to not having a post or anything to mount anything to.:-)
