It's not my build; I have a Pompetamine, and the Hope Singlespeed hub (135mm OLN) already has room for 4-5 sprockets off a 9/10-speed cassette. mechanical_vandal was thinking of using DuraAce, so DXR would match the quality.
You can get a 6 speed cassette on there, modified from a 9 speed. My mate runs 6 gears with one on his trials bike. I've got the same hubs on my Pompetamine and planning on going 6 speed in about may when I sell my road bike. Was planning to use one of these but there seem to be a few good alternatives from Fire Eye on Chain Reaction.
You can get a 6 speed cassette on there, modified from a 9 speed. My mate runs 6 gears with one on his trials bike. I've got the same hubs on my Pompetamine and planning on going 6 speed in about may when I sell my road bike. Was planning to use one of these but there seem to be a few good alternatives from Fire Eye on Chain Reaction.