5 point harness in a car w/o roll cage...How to do it?

They do make Harnesses that are floor mount.....I have them in my car.....but like stated they forces exerted can hurt you in an accident. Mine are a Y type that have a long strap the bolts to the floor.....the problem is that they pull down on the back of the seat and if your shoulders are above the seat they pull down on them.....I don't waer the shoulder straps when driving on the street just the lap belt.