If you've ever been in a Camaro (or any 2+2 coupe)...you're familiar with this situation. The huge doors limit what they can do with the belt position, unfortunately.
The magnetic straps could probably be a little stronger, but personally -- it never came unsnapped while I was driving the car...so I can't really comment there. The alternative, however, design-wise...is something fixed and ugly like this:
http://l.yimg.com/dv/izp/chevrolet_c..._frontseat.jpg