Definitely no clearance issues. Could have went with 28.5's with no problem there. I do have a little trouble turning my 27's in thick mud in high gear. In low gear I have no problem though. My 500 is totally stock. When I start doing some mods, I'm sure it will help. The AC is the best in the mud that I have seen. The only others that can hang with me around here is kawasaki brutes with 28.5's.
First time I took it out, I broke the front differential BUT they fixed it and hasnt had any problems since. I give this machine hell. I ride in a lot of water and mud.