Mine is a 40 sport size. It has an Enya 45 on it which is a light engine at 15oz. but it is not too much power. GP airplanes are way too heavy . Most of my planes are Sig or something I cut my self so they are usually lighter. I have seen one with an OS 70 on it . The 40 size my say slow poke but it flies about like most 40 size sport planes. Most fun fly planes will fly much slower. It is cute like some of those Lazy type airplanes. Even if you add a bunch of weight be sure to get it balanced far enough forward so it wont be crazy to fly. I thought I might build one of those Slow Poke park fliers. Now that looks like a bunch of tooth picks. Good luck with yours mine now has about 50 flights on it . It is a Little hard to fly in much wind especially landing in a cross wind.