I had a 2004 Bigfoot 25 ft. rear queen. Had it numerous times in the high desert of Oregon, temperatures up to 105 degrees. The combination of reflective double pane windows and a minimum amount of interior cubes allowed the trailer to cool extremely fast with a 13.5k unit. Holding 70 in 100+ degree temperatures was not a problem. We would caravan with a group of other couples. The women would sit in the Bigfoot with the air on drinking wine while waiting for their rigs to cool down. The outside air was dry if that makes a difference. The nature of the hull design allowed that the air conditioner could not be ducted and just blew from the ceiling. As stated above, the insulation isn't that thick but the lack of studs and roof joists means that there aren't many heat gain pathways.
We had more issues with the cold rather than heat as moisture management became an issue. Once we figured it out things were good. They are tight and pretty much impervious to whatever nature wants to throw at it. Mine was in hail and severe rain plus an encounter with a tree branch, no damage.
They still make the 25 ft (22' box) model. Unlike the Oliver, a Bigfoot is 100" wide so room for a full bath and walk around queen. FYI, brochure weight was 4,800# but in actuality dry weight was over 5,200#.
