I wouldn't recommend it at all. Sorry, but the 5th passenger needs to call "shotgun" sooner on the next trip! Granted another belt can be installed, it would have to be a lap belt only which you may think is better than nothing but, in a serious accident, the lap belt alone without a shoulder belt can do a lot of bodily harm. Then again without a belt of any kind, ejection is likely. As Shelby427 mentioned...lawsuit, a very real and unfortunate reality these days. I could go on and on... I'll end with- DON'T DO IT!