The Aeromod Loadstar Model 100 was a biplane conversion of the Piper PA-18 Super Cub? It’s proof positive that people will take a thing that’s this close to perfect and try to make it…better? 

Known as the ‘Aeromod Loadstar Model 100’, this Biplane conversion of the Super Cub, powered by 135 hp (101 kW) O-290-D engine, was designed for improved capability from high-altitude airfields.

This was reported to be the only factory PA18 bi-plane, (The STC was installed at the factory). It was a 135hp and still had all the attach points on it. The current owner was about to rebuild it as a standard PA18-150, so the only factory Super Cub bi-plane is probably no more. It was kind of like a baby cabin Waco.
Some have expanded on this idea to make their Piper more unique.