I have a 9200 also, and it is a meat locker within 5 minutes with temps outside in the 90's.
A roof 14 inch square opening is standard, almost all, if not all, ACs will fit in this hole. Then you have shore power power supply in the form of household wiring. This wiring should be just stuck somewhere in the hole area.
Put your AC unit over the hole, connect the wires etc and you have AC.
Beware that maybe the higher capacity unit might weigh more and most FG shells do not like a lot of weight
up there. Over time they can sag.
Use a new gasket each time.