I converted a SRAM 3 speed to a fixed 2 speed and installed on a 5 foot giraffe this spring. The SRAM is suppost to have a lot less slop in the gears (about 1 degree). Still very difficult to ride at first. See the article Converting the Three-Speed Sram Torpedo Hub to a Two-Speed FG Hub
by Graham Webster.
http://www.fixedgeargallery.com/articles/grahamwebster/grahamwebster1.pdf