I had same problems as JRS. I settled on Denman tires, load range E. I was going to Alaska last Spring and worried about the D range tires that came on my 5'ver. I towed about 12K miles on the Denman "E" tires, over some really nasty gravel roads (my Brother in Law, who made the trip with us, burned 3 of the "D" tires before he broke down and bought "E" tires in Anchorage, Alaska. No problems after that.
The Carlisle's are now made in China... . I know because the tire dealer ordered them in for me and I would not accept them... he bought the Denmans and charged me $2 a tire more... they were made in Mexico... .
The RV manufacturer's put tires on trailers that are just not heavy enough, I feel.
With 16" tires, you have to change the hubs/axles and that opens a whole new can of worms.
Florida Ed