dtfoster do you have the 22.5" rims or the smaller 19" ?
The big thing is the weight and size of the tire as you will have to mount and remove it by hand.
Not much room underneath.
I have seen at the RV shows a special adaptive spare tire hitch that can be mounted with modification to the existing receiver. It can handle up to the larger 22.5" rims and tires.
Here is one from Roadmaster that makes removing the tire easy with a swivel bar bracket.
I do know it's about $600 plus installation.
http://roadmasterinc.com/products/spare_tire/index.html