You opted for "manual adjustment" over an automatic or "spring tension" I see. Pro's and cons to each. I debated on doing something similar (tensioner) but ended up "anchoring" my jackshaft, and slotting out the engine mounting plate some more, in order to move/adjust it forward as needed, and making a pair of rear axel tensioners to pull/adjust the rear wheel back. BUT, you've got the more critical, and less forgiving, drive chain(s) to deal with, and a lot less room to do it. Not to mention the significant increase in H.P and torque transfer using chain drive over belt drive. Pretty cool. Matter of fact, I just watched Mecum motorcycle auction this weekend on T.V., and saw a few of the old "Board tracker" bikes of the 20's/30's (of similar design going for INSANE money)...Hard to believe that those guys usually didn't even have BRAKES! (ALOT of racers AND spectators died back then!) Crazy speeds on a 60degree wooden track!