I have had a few people ask about 31" tires on a Carbon Cub. I finally threw a spare set on and I have some feedback. I have the the 3x3 gear and bigger brakes so CG was a concern. It moved it .25 inches forward, which means I carry a little ballast in the tail if I am light. My gross is now up to 961 lbs. The tires have a bit more side structure and I could feel it on the very first touchdown. They also are much easier to hydroplane (I don't even have a theory here, they just feel smoother and inspire more confidence). For the stuff that I routinely do I would say its probably nice to have the heavier sidewalls, but I also go on some pretty rough/off camber stuff. They raised my prop 2.5 inches at similar PSI and That is a nice benefit as well. All in I don't really know if it is worth putting on unless you go and do rough stuff routinely. I will be keeping mine on for a while just to play around and see. Below is a link to a video of some hydroplaning on the new 31"s

http://www.youtube.com/user/lameusernameguy