I am ordering an '08 Blk Mrkt Riot frame but cannot decide on a size. I haven't seen anyone with one where I live, so I can't test any out. I'm 5'8", 5'9" with shoes on, have a 30" inseam, and a mountain biking background. I assumed the 21.5" TT would be fine, but after checking that size against the regular or medium sizes of other dirt jump frames, I'm not so sure anymore. It seems most dirt jump frame TTs are closer to 22". What do you guys think? I know it's only .5" difference, but there must be a reason Blk Mrkt chose those 2 sizes. Thanks for your help.