How to properly install roof top ac - Dometic Rooftop RV Air Conditioner

I put a new roof on my 93 Coachman motorhome. When I pulled the A/C unit off of the roof there was a seal around the opening and 4 additional 2" X 2" styrofoam blocks near the outer edge of the unit near the corners, it was hard to tell. Do I need to use there blocks when I re-install the unit or just use a new seal. I can't find any reference on the web about these blocks so I am tempted to install the unit without them. Any ideas? I put a new roof on my 93 Coachman motorhome. When I pulled the A/C unit off of the roof there was a seal around the opening and 4 additional 2" X 2" styrofoam blocks near the outer edge of the unit near the corners, it was hard to tell. Do I need to use there blocks when I re-install the unit or just use a new seal. I can't find any reference on the web about these blocks so I am tempted to install the unit without them. Any ideas?

Normally you have a 14" square opening for AC to sit on. (same size as any roof vent opening as well.) As long as that 14" hole is framed solid so as to allow the AC unit to draw down evenly, there shouldn't be a need for anything else. Gasket of AC over the hole evenly and ceiling assembly inside, then tighten down until gasket is approximately 50% of original thickness. You did buy a new gasket right? Old one peels off, but may take a little extra scraping if it's been on there since original. Clean surface of AC good and stick new one on in same place. The only reason I've seen extra supports is if unit sits too high due to shims added between roof and frame. Sometimes the roof has started to sag in that area, so they shim between frame and roof material to raise it slightly so water doesn't sit at gasket area when wet. Otherwise, tighten down as instructed at those 4 bolts and so gasket is compressed evenly all around and your good to go. Normally you have a 14" square opening for AC to sit on. (same size as any roof vent opening as well.) As long as that 14" hole is framed solid so as to allow the AC unit to draw down evenly, there shouldn't be a need for anything else. Gasket of AC over the hole evenly and ceiling assembly inside, then tighten down until gasket is approximately 50% of original thickness. You did buy a new gasket right? Old one peels off, but may take a little extra scraping if it's been on there since original. Clean surface of AC good and stick new one on in same place. The only reason I've seen extra supports is if unit sits too high due to shims added between roof and frame. Sometimes the roof has started to sag in that area, so they shim between frame and roof material to raise it slightly so water doesn't sit at gasket area when wet. Otherwise, tighten down as instructed at those 4 bolts and so gasket is compressed evenly all around and your good to go.