Yes, the manufacturers do allow for pin wt carrying part of the load. You don't mention the brand name tires that you've had issues with. There are better designed ST tires out there, that likely will give better service.
IMO, load range E should be a good choice, while inflated to handle a full load. To ME, this is better than going to a heavy higher rated tire, then need to lower pressure, causing more heat, or tire scrub.
Take a look at the newer improved, higher speed rated ST tires, such as GY Endurance, Provider, or Carlisle HD, which are nylon wrapped, higher speed rated, and a better choice than most ST tires.
Jerry