The XPS Rib and Duravis R250 are the best all steel ply tires. Both have a rib style tread that is very good for trailer position. I have ran the Rib for 6.5 years(one set)/40K+ miles and now the R250 for 3 years. The R250 is about 50 bucks per tire cheaper.
In a poly carcass tire Bridgestone makes a true commercial grade tire in the Duravis R500 HD. It has a two ply poly carcass where most other poly carcass tires are single ply.
What is your axle spacing center to center. The LT235/85R16E is an inch larger in diameter vs the ST you have now. You need 33" center to center or more to run the LT235. The LT245/75R16E is closer in diameter, however a bit wider.
Is your 11-11.5 GVW or axle weight. If that is GVW then you could also look at LT215/85R16E rated to 2680 lbs and 30.5" diameter. What is your GVWR for the trailer?
Chris