Aye, have to take them off to reverse too. And to get things from the glovebox. Wouldnt get them again, unless i could have normal seatbelts too, or if it was for an out and out track car. 4 point 3" harnesses (with fighter pilot style buckle) hold you in soooo much better, the seat belt clip type ones are a bit of a compromise.
Mine are mounted to the subframe by the handbrake, and to the seatbelt mounting point behind the door. In the rear, mounted to rear seat belt mounting point. Not sure where you'd mount them too at the back of a vee though mate!