I have a Nash 25-S travel trailer & 3 of my friends have Nash products that are a bit smaller than mine, also. All of these trailers came with Goodyear Marathon, 205/75/15-C tires.
I did a little research on trailer tires, after my buddies 24-A blew out 2 of them on a trip, back east.
The older Marathons were constructed of polyester & steel plies on the tread belts. This combination would expand, when hot, & cause separations & consequently blow-outs.
A few years ago, Goodyear upgraded their tires by adding a ply of nylon on the outside of the poly/steel tread plies. The nylon does not expand, when hot, & acts like a "girdle" holding everything together. Since then, none of us have had a problem & we don't seem to hear of nearly as many separation problems, as before.
There is another tire called Tow-Master by Greenball. It's actually made for them by Goodyear & goes down the same assembly line as the Marathons. Has the same tread pattern & parts make-up. The only difference is the name on the sidewall. They just use a different die when making them.
Since you are not paying for Goodyears advertising & the Blimps, these tires are much cheaper. Look for a Greenball distributor/dealer in your area.
All of us were able to go up two tire sizes to 215/75/15-D. They fit in the wheelwells very well & are not too close together.
I've had mine cross country & into Canada & live in the Phoenix area. It's 109. 4 degrees outside, right now. I've had mine for a couple of years, now, with no troubles.
Just a suggestion.
Joe F. (Buffalo)