Ours are 1" and seem to be sufficient. Originally they were not installed correctly and there were massive gaps in the corners. When pushed up into the corners the seals were then far too short. I informed thor and they sent me enough new material to seal all the bays. The other place water was coming in was around the frame rails, where they enter the bays. Expanding foam took care of that.
Vicki and Mike, Aria 3901- The Wined Up Bus