Gp Pitts I Got One--see The Pics
One thing I have noticed is that with the light glow engines there is a lot of room for weight distribution. It was noted in an earlier post that with the OS 1.6 the servo was mounted right behind the firewall under the cowl. That is weight that can be moved way back in the fuse is you a heavier engine. Also there is a lot of movement for the battery (or batteries) in the fuse--also a lot of room to move a smoke system around in there. I am a firm believer that GP recommends the US 41 only because that is the engine they sell and not because it is the right gas powered match.