Besides the tires, the Rockhopper also has the front suspension that is a pain when stopping and going. I have looked at frame size. I was at a LBS today and the guy suggested a ~50cm. Beyond that I am not sure. Most of the bikes on CL seem to be 58cm or bigger. It is like trying to find pants with a 27" inseam, forget about it. Actually the size frame that worked best on the straddle test (straddle, should have an inch before it hits) was a 43cm, but everything else was too small. How much does the fitting stuff people talk about cost?