DuvalBirder -
Re your question about whether 15 inch tires will fit without a lift kit? Use the Search tool to find something called the 3-inch rule. You can start with
http://www.trailmanorowners.com/foru...ance#post50343
and posts #3 and #8 here.
http://www.trailmanorowners.com/foru...ad.php?t=13070
Finally, if the 3-inch rule suggests that clearance is a problem, and the idea of a lift kit is getting to be too complicated, there is another approach described in Post #7 here.
http://www.trailmanorowners.com/foru...ad.php?p=44983
As for Duro tires, I'm not sure I've heard any useful feedback here on the board. Let me offer three pieces of general advice, regardless of brand.
1. Be sure your tires are rated Load Range D (LR D). There are some 15-inch tires that are only Load Range C (LR C).
2. The tire size number string should start with ST (Special Trailer), not P (passenger) or LT (light truck).
3. I like Padgett's advice to buy a tire with a nylon overlay or nylon cap or nylon ply. If a tire has one, it will be called out on the tire sidewall along with the number of plies.
Duro has ST 225 tires rated both LR-D and LR-E. They are the same physical size (larger than your current tires), so if you are going to choose one, I would say "In for a penny, in for a pound" - go with the E. But if clearance is a problem, and you want to avoid putting in a lift kit, Duro also has a smaller (205) D-rated tire, about the same size as your current tires.
Good luck with it.
Bill