I replaced my four rear 295/80R22.5's with 11R22.5 in March, 2011. They are the same diameter and nearly identical revs/mile, so work fine. Cost a bunch less and 11R's are usually readily available wherever you may be.
However, I can't use them on the front because they have less load carrying capacity than a 295/80 LR H and my front axle is heavy (14,600 lb GAWR). I would have to use 12R's there, and that should not be a problem even though they are a bit larger than the 295/80. I have Goodyear G670's in 295/80 LR H on the front now and they are good for another three years, so haven't made any decisions yet.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC