Actually the GP Stuka has the engine mounted at a bit of a downward angle which puts the standard muffler exhaust out the bottom. I was concerned about the engine running in this position but it hasn't been any problem. I agree against trying to run a 2 stroke inverted. Too many problems to make it worth while. Any of the warbirds with round cowls can have the engine mounted sideways which allows an incowl muffler exhaust pipes to blow straight out the bottom. Suggestions are the FW90, Zero, Corsair, Texan, P47, and Sea Fury. I have a Direct Connection Sea Fury which flys really nice and has the engine mounted sideways. I don't think they make them any more but Top Flight makes a Sea Fury 60 kit. Nice thing about bottom exhaust, very little clean up. I only have 1 tiny spot on my Sea Fury and my Stuka that gets any exhaust oil. A quick wipe and its clean. Zeros are also fantastic flyers if you can get one. [8D]