YOu need to be careful with adding too much A/C. If you have too large, or to many A/C the unit will cool down before it has a chance to remove humidity...you wind up with a cool clammy RV which is very uncomfortable. The A/C is sized for most applications, and yes, if your going to be camping in 100 degree temperature, it's going to be hot. Here in AZ on a day when it reached 105, the interior of my car after only being in the sun for about 15 minutes was 124 degrees. You have a metal box, with hot air on all 6 sides, with windows, doors, sky lights etc your not going to cool it to 72 degrees. I don't know about all units, but Jayco does offer upgrades to larger A/C or a second A/C on many units. Myself, if I knew how I was going to use my RV I would do my due diligence to check and make sure it would work in the climate I planed on using it. There is so much information (including here) on the Web it's very easy to find information on others actual experiences.. I hope you can find a remedy to your situation. Good Luck.
2011 Toyota Tundra double cab