My fixed conversion started with 27's. Had my LBS order my a rear 700 wheel thru QBP. It is a surly flip flop laced to a Mavic Open Pro. Bought a 35 dollar front wheel they had hanging for ages (RSX hub to arraya rim). Both wheels are wearing Specialized all conditions 700x25. I was lucky, the original brakes had enough reach.

Before the bike standover was just a bit tall for me. Changing to 700's made it to where the boys didn't sit on the top tube. I have yet to experience pedal strike. When I have the power grips on the bike, the section of strap that hangs down tends to scrape in tight turns. Oh and I'm running 172.5 Sugino cranks.