Like the OP I am looking for new tires. My problem is, I have 4 load range C tires rated at 1820# per tire or 7200# per four. My TT has a gross weight max of 7700 # so I guess the factory assumes at least 500# on the tongue. :h Fortunately I do not come close to the max load.
My plan was to switch to load range D but I have not yet found an ST 205 75 R 15 in that load range. According to the internet they are out their but I have not found a local source.
Since the objective is to pick the best third world country you wish to have build your tires; I plan on dealing with my local tire guy and getting the full replacement guarantee.
If you look up “Tire Safety with Roger Marble” on the web you can get a good overview of tire types and functions including blowouts.