ST tires are rated at max load
LT tires are rated at 80% of theoretical max load, because of the continual varying load of the intended vehicle and the lack of knowledge of tires in the general public.
I have run LT tires on all of my trailers since the 90's. I usually wear the tires out long before aging out.
I actually run MT tires on our fifth wheel, load range J. When it was time to replace the LT Hankook tires, it was suggested to me to look into the 17.5 MT's. I researched and found I could purchase new steel wheels and tires for $5.00 more per wheel than it would cost for new tires alone. I jumped from a 3750 pound capacity per wheel and tire combo, to 6005 pounds per wheel and tire.
I was having issues with the 16" wheels, cracking and welds breaking anyways, so I stepped up to the 17.5's. That was 6 years ago, haven't had a tire or wheel issue since.