I didn't think V belts sliped much upon acceleration with these smaller engines. Shows you learn something everyday. Means I have my work cut out for me with my belt drive idea.
I think the key is to have the sheave aligned perfectly on the rim (I measured from sheave to rim all around the rim to get the sheave totally centered). Once its aligned perfectly & tightened down, it wont move. Then you can tension the belt tightly (I use a skatebord wheel) & there wont be any loose spots as the wheel & sheave turn in synch. Pedal assisting from zero to rolling speeds also minimizes belt torque.
-Alex-