Don't do that, the belts need to be mounted straight back from the top of your shoulders.
If you mount them to the floor, can you say spinal compression?
I ran the crotch belt through the seam in the seat bottom. My wife sewed it up.
I know crotch belts aren't comfortable, but they really keep you safe in an accident.
And why do they call them anti-submarine belts? It's not like you don't know the belt is in your CROTCH LOL!