Woodsy,

Where can you buy/order one? How much?
Wouldn't think of building an ultralight without one! An engine that wouldn't taxi an ultralight on D/D will fly one fine with a reduction/larger prop.
As far as "why" everyone so overpowers their moidels these days, the market was lost for these units-just buy a bigger engine for the money you'd spend on a gearbox/belt drive.

Jetts