Thoughts to consider:
If you carry an unmounted tire, it will require very close to the same space as a mounted tire would.
Not all roadside services are equipped to dismount and mount a tire but all I have used can change a tire already mounted on a wheel.
Many places I RV/Camp are not near any towns or cities and even in this day and time I find myself in locations without cell service which would make it hard to obtain any roadside service even if they would come out to a remote location.
If you have a high capacity hydraulic jack and proper tools (large, long breaker bar or electric impact) then it is not as hard as it may seem to change a tire. Proper techniques make a huge difference.
If you don't have a mounted spare, and only have an unmounted tire (or none at all) and a good samerican (such as myself) sees you stranded on the side of the road he may stop in an attempt to help you but unfortunately won't be able to help you. Perhaps he will make a call for you later if you are in an area with no cell coverage.
My thought is that it is better to have a mounted spare and not need it than it is to need a mounted spare and not have one. I would only suggest to not have a spare only if you plan to always be RV'ing near a city or town with services easily available and even then I would prefer to have one.
Last thought, as most know you should have the same tires all the way around but for sure matched for each side of the dually tires, with that and you don't have a spare and the roadside people bring out a tire, will it be the same mfgr as what matches what you already have? Keep in mind that even the same numerical tire size may have a slight difference in circumference between brands. ~CA
