Lots of time the issue with chopped tops is with getting the glass cut. Cutting curved glass is an art form, and most guys freak out when the find out how expensive "art work" is. You see guys sinking glass into the body and laying back the glass and a bunch of other stuff to avoid having to cut the glass.

Many guys are also bonding the glass to extended window pinch welds like most of the newer cars are done. Rubber tends to break down or not always seal against the glass. Gene