Welcome to the forums Driftless. Speaking of tires I would highly recommend Greenball Towmaster. I did alot of research on tires for my Airstream as I do not want one of my fenders ruined because of a crappy tire. I searched numerous sites on the internet for travel trailers, boats, and cargo trailers. What I learned is to stay far from carisle there junk, Goodyear Marathons you have people who swear by them and people who absolutely hate them. Now with the Green ball you have more people satisfied and few who had trouble. I will stick with Greenball its what I'm running now. Just got back from a 2400 mile road trip, absolutely love them. Just make sure there made in America and not China. Also I'm running ST 225 75 15 tires switched from 7.00-15 LT. Found out I had to let the air out of the tires to get them into my wheel wells, which would be a nightmare if you dont have a compressor on the side of the road and need to do a tire change. When I need new tires again I will probably switch back to LT, but do love the radial just not the air thing. Another thing I read was you should replace trailer tires every 3 yrs regardless of how many miles you have on them. A couple hundred bucks is alot better then a couple grand in repairs to your wheel wells.
Heres a story for you my buddy who runs a crew for Anderson windows purchased a new cargo double axle trailer was putting right around 9000 lbs a day in it from old windows new windows and all kinds of tools well he ordered the trailer thinking he was getting 2 5200 lb axles drove it for 2 years tires started getting bald from the abuse next thing you know one of the axle shafts broke, turns out they had put 2 3500 lb axles on it (in case your wondering the axles were from alcoa) Tires never had any problem. I'll give you one guess what kind of tires they were.
Anyhow I hope this helps as it stressed me out when trying to figure out what tire was good enough for my coach.