ahh thanks.

now i really should think about this project. forget the bmx freewheel i want fixed cog because i want to be able to brake by back-pedaling. yeah seeing how the threaded fixed cog will be too far in toward the hub the chainline must be really messed up. reason i was planning on doing this is to salvage my old parts, a hideous specialized m2 frame (some may recall the threads i posted earlier on this frame) that probably has a misaligned rear triangle, and a 7sp freewheel wheelset. i want to be able to brake by backpedaling just like the old days on my 20" wheeler and make skid marks . might be too much trouble than it's worth though, i just finished building my freehub SS and it's a lot of fun to ride!