I have a convertible with shoulder belts. What you should know is that there is no give to these belts like in newer cars. You are literally strapped into the back of your seat, and cannot lean forward to check your mirrors fully, change your radio station, or adjust the heater controls, nothing. I don't wear it for this reason. It's like being strapped down like a criminal in an insane asylum. So, if you do this, try to rig up something that would have a newer like spring setup seatbelt, so you don't restrict your movement so much.
