RE: OS 300 Twin plane suggestions?
I had the same dilemma with an OS FT160 twin. I shoe-horned it into a 90-120 (4stroke) sized GP Skybolt kit, but it proved too much for the tail to handle. I ended up putting it into a 120-160 (4c) sized Spacewalker. It flies the plane ok, but the plane itself isn't terribly exciting in the air. I'd recommend that 1/3 scale Pitts for yours, you'll get more fun out of it than the 1/3 scale Spacewalker.