Our last coach had just two roof airs (plus dash air) and we took a trip thru Yuma and the low desert last summer. It was around a constant 118-120 degrees and the coach was nice and cool the whole time. I never shut it off in fear that we wouldn't be able to get it cooled off again but i'm thinking maybe the roof airs are the best best overall for consistent maximum cooling. Engine temperature continued to run within the normal range (even when we got to the Santa Ana mountains) but i'm wondering with an OTR type system if that would have been the case. Downside of course is the genset running constantly but that was worth it to keep everyone on board happy.

PS: still jealous of everyone with OTR of course