While I can't speak to your coach, many have different wheels for the front and rear. That would make carrying a mounted spare more difficult since you wouldn't know which wheel to put it on. Carrying an unmounted spare (still over 100 lbs) may not bring much relief if you can not find a service that will mount it along side the road.
Than, of course, you still need to replace it periodically whether or not you have ever used the tire.
With all that in mind, I prefer to carry a Coach Net card and be prepared to purchase a new tire at the time....plus save the bay space.