If you do attach it to the cab, I would highly recommend mechanical fasteners over tape, VHB double sided tape, or even glue/epoxy. If yer squeamish about drilling into yer cab, yer gonna have to find a strong method of attachment. Even some bracing to aid in keeping the form from distorting from the air flow.
Bed based will require either a cab gap (like the T-150 has) or a sliding cover as the truck flexes. My front top/side covers on my aero cap slides over the cab.