We have a 19 year old 2.5 lb chihuahua that is blind. Of course, she has to go on us when we camp as my missus won't let a dog sitter be entrusted with Pippie's care. I will never try and make my wife choose between me and Pippie as I am afraid I would be full timing up in our trailer when parked out on the property!
Anyhow, we have to camp within a hundred miles of our home right now as Pippie isn't a great traveler. In the summer, we see triple digit temps and little shade. My 2002 Cougar 278EFS A/C worked fine except in triple digits and direct sun and then the insides WERE hot. Had to fix that.
Step one. Replaced non adjustable vents. While I was up there I put the styrofoam stuff at vent ends to block cold air from traveling into the ceiling void. Helped some.
Step two. Got some foil tape and taped void between vent and duct; it was done poorly from the factory. Helped some.
Step three. Cleaned A/C fins up top and cleaned down below. No difference as it wasn't bad.
Went camping and it was still miserable; could hardly get temps in cabin below 82-83 degrees in direct sun
Step four - Went to Best Buy and bought an 8K BTU portable A/C (still at camp ground). It helped some and we could just get cabin temps under 80F but it was now endurable.
Step five - Got home and bought a Dometic Brisk II 15K BTU it works better; can get temps in the high 70s in direct sun/triple digits. Haven't used the portable in conjunction with the new A/C but will haul it with us... just in case next weekend where temps are going to be triple digit again and no shade.
Step six - Spent the weekend putting adhesive 20 percent film on the windows. This is supposed to only allow 20 percent of the light and UV and thus, the temps that result from heat transfer through the windows. I bought a 50' roll on eBay and a set of install tools from Amazon. Cost about $75 total.
We shall see after camping next week on the Nueces River in Camp Wood Texas (spot of the original Garden of Eden I think). I had also changed out the skylight in the bath from clear to smoke colored and not sure if that will help and if not will have to figure out what to do there as that skylight becomes a real source of heat during direct sun. We also have a desk top oscillating fan that helps; had a tower fan but it died.