The 285ts has a lot of glass area so adding the foil bubble wrap makes a big improvement in daytime cooling. It is also very easy and fairly inexpensive. Also, that big dining area slide provides a lot of heat gain. It is not as well insulated as the main coach is. The floor has no insulation other than the (thin) carpet. Just a piece of 1/2 inch particle board. The roof is also thin. A 15000 AC should cool that space easily but I thin it is the glass and slides that make it difficult. I did replace the bathroom AC vent with one that will "almost" completely close as it was getting too much air. I try to avoid camping in 100+ degree weather but sometime on the way out or home, it is just necessary. Temecula should be a pretty good test.