Way back in the hayday of ultralights a local Lazair builder and flyer decided to increase the efficiency of the propulsion system by designing and constructing a belt re-drive for the 185
This allowed the engine to turn a much bigger propeller, I was fortunate to find a lazair with this configuration, built by the planes owner who copied this fellows design and improving  the conctruction by casting the parts from molten aluminum.

 I have first hand knowledge the increased performance of these units, since I have mounted them on my float plane, and can tell you they make a marked improvement on take off from glassy water and increased climb performance not to mention quieter too, off floats the plane will take off in half the distance!. They swing a Colin Walker 44x22 @2800rpm  1:1.9 ratio