I'm glad I saw this thread before doing anything stupid. I was planning to go out and buy a BMX wheel to replace my even quicker-and-dirtier method for single speed on my Dahon Boardwalk D6 (i.e. removing the derailleur, picking the gear with the best chainline, and shortening the chain). Who is this Peter of Design Mobility of which you speak? $55 sounds like a decent price, and I'm curious. Does he do fixed, or just SS?