There's a lot of slop in the top mounting on a targa -- plenty to keep it from binding under any amount of flex that would be considered normal...when mounted there is at least an inch to the back between the top structure and the roll bar. The vinyl part of the roof is tighter tolerance but it can flex also so not a problem.

Good thought though. I don't have a cab but would imagine it's a similar story there.

I put on my Targa top when keeping the car jacked for extended time (like an engine drop). That seemed to reduce the flex and ensured I could open and close the doors.