I personally don't think WWII warbirds fly that well to begin with. You really begin to notice the heavy wing loading after flying a nice, low wing loaded plane like a Stik or 3D bird. Adding retracts will only make it worse. If you are looking for that clean look with gear up, go with a P51BL from Parkzone. It'd designed to belly land and is reinforced in the proper areas from the factory. You just hand launch and your away. It's lots of fun, nice, and moderately quick for a little foamy.

PS....retracts are a major pain the butt IMO. You will always be messing with them.