Duraplanes
Personaly I don't consider the duraplane a trainer in any other sense than it's durability. It doesn't fly like a trainer, it's fast and maneuverable, can perform more aerobatics than a conventional trainer and lands like a brick. I would not recommend one for a pure beginner to learn on unless they have no choice but to go it alone.
Only attempt such drastic modifications if you are qualified to do so.
Where would we be if Orville and Wilbur had never made modifications to those bicycle parts?