Thank to all for your responses, I am going to get a new pair of Kendas (213.90 for two tires on new wheels), slow to 60 mph on days over 90 deg F, get the trailer weighed the next time we head out, and be sure the new tires are at 65 psi before we drive. I dont think I want to try my buddies' scheme of lowering the tire pressure in summer, too much risk there.
Thanks also for the link, "All I could aford", I will keep that and perhaps try some Westlakes for my next tires, if we still have the popup in two years. BTW we are looking to move up to a 27-30 ft TT, in the future.