i moved to japan about six months ago. and, since the roads are flat and i'm sick of adjusting my derailer, i've chosen to build a fixed-gear. actually, i'm looking to build something with a flip-flop hub. so, since i live about an hour from the keirin/gan wel pro factory, i think i'll pick up a track frame there. in which case, what do i have to know about bottom-brackets and hubs? i guess the hub just has to be the right width. but does the bottom-bracket have to be a japanese one? any advice would be greatly appreciated.