He uses 175 mm cranks in the dirt for torque and shorter ones on the road for a faster spin and higher cruising speeds. He was asked about building up a unicycle with a Schlumpf two speed hub, but he says they are only available in Schlumpf's own unicycle for now (with a non-standard hub spacing), it would be expensive, and he has reservations about any setup that would let you get going any faster than you could outrun if you stepped off the front (which does occasionally happen with a unicycle, especially when you least expect it!).