Oh, and smallfurry, personally i'd run a singlespeed chris king hub with 5 cogs from a regular cassette....run your centre gear as your regular singlespeed size...then 2 pretty low ones for extreme ups...and two pretty high ones for extreme downs or getting to the trails via the road.
You can then ride it pretty much like a singlespeed but have bail out gears should the terrain change dramatically...also means you can set your chain so that the rear mech is nice and tight on the biggest cog and not flopping around on the smallest.
Oh, and smallfurry, personally i'd run a singlespeed chris king hub with 5 cogs from a regular cassette....run your centre gear as your regular singlespeed size...then 2 pretty low ones for extreme ups...and two pretty high ones for extreme downs or getting to the trails via the road.
You can then ride it pretty much like a singlespeed but have bail out gears should the terrain change dramatically...also means you can set your chain so that the rear mech is nice and tight on the biggest cog and not flopping around on the smallest.