work it from the top
The big problem for many is just getting the AC up top. If you can do that, then attaching it is easy. Set it in place on the 14 x 14 vent hole. Use Vulkem seal and tighten the four attaches. Elec and drain line are standard...and in the AC instructions. Use a few padded blankets for your sitting area and stay centered....you won't dent the top.
"If it can't be reduced, reused, repaired, rebuilt, refurbished, refinished, resold, recycled or composted
then it should be restricted, redesigned or removed from production."