Heat Box - straightening out fiberglass?

The support rod there has a predetermined thread length. It must compress a seal to the cowl but cant be over tightened. Given its location, I really don't think the rod could warp the fiberglass even over a long period. The seal fails too so...
If the box is prone to bowing, the door opening is the weakest side.
I'll bet my quarter that the box has always had about the same amount of bow there.