i don't know anything about jacking a motor while moving it forward, but marcus does (pic on page 2). we were yakking about his bike at the okemo event (nice build btw) and he mentioned swapping out the driveshaft from a different model for a specific reason that i forget now.
i'll be seeing him and the gang saturday, more racing.
r75/6 (mine since 1980 - thx lloyd!)
900ss/cr (sp spec)