If you haven't seen mine in the other threads. I built mine last winter with hub gears, and just went fixie 2 weeks ago - it's great.
Before that it was running a SRAM spectro 7 hub which was also cool. you may tell by my photos that I was tentative about running a fixed rear wheel - hence the fact there's still the gear clickbox, back brakes and general cable-age still going everywhere.
Anyway - now it's running 12t -> 54t but I've got a 56t chainring on order to make it a bit longer legged. I ride it 8 miles a day across London UK and I love it.
One thing - whatever you do to your Twenty- it will never be superlight! You could counter it's girth with *everything carbon* but it still will only be a lighter 20 not a Bike Friday or Moulten SP. It will, however - be amazing fun.
Be sure to post any pictures when you get to it...
Oh - if you go over to
www.fixedgeargallery.com and do a "google this site" for 'raleigh twenty' you should find a few more of these Nottingham beauties!
Huw