"AikenRacer".....When I owned my Diplomat (non tag) coach, I carried an unmounted spare in my main bay. It was a small diameter 22.5, so it fit.
When I bought my current coach, I had no room for a spare, but I'm not as concerned about needing one with this coach. Here's why.....when a tire repair company comes out, they often will not have the same size tire and brand as what you have on your coach. Consequently, you either end up with a mismatched front tire or a dual that is smaller or larger than your other dual. Both of these issues will require immediate attention and the purchase of another tire in your size. Sometimes you do luck out and get a match.
When you have a tag axle, you can pull off one of the tag tires and replace the front or the dual and have a matching tire. It's not a big deal to put an odd ball tire on a tag axle. As a matter of fact, I would leave it there until the trip was over. This really gives you some freedom with the type of tire the repair truck brings.