[RipNC]

Ok, this would have been the winner if I hadn't completely sealed and insulated the 14x14 hole and didn't need to leave the control boxes up above the plenum trim. The plenum trim has to stay up to support the 2 control boxes that are completely wired up.

I had considered a similar though compressed by 2 - 4" solid concrete blocks. The thought of the blocks somehow hitting TPO scared the idea out of me. We used to put TPO on our warehouse roofs and it was many times heavier and still a PITA with leaks every time some HVAC mechanic was on the roof. Went back to good old fashioned 5 ply built-up roofing with 25 warranty on every building, much more $$ but it lasts.

May wind up implementing this idea if the stuff i just bought from HD doesn't hold up. Even if I have to take the control boxes down.

Now if only I can find the unit to buy...