It should not be a problem using the engine at any position on a plane. Fuel tank location and how far away it is from the engine can sometimes be an issue though. But if I remember correctly, OS put on a carburetor that has a really large venturi opening in it, and that affects how well it can draw fuel. Especially with larger propellers where the engine doesn't turn RPMs as fast as with smaller props. Many of the Pitts mufflers do not have enough back pressure or muffler pressure to help the engine draw fuel. Usually with the Pitts mufflers you have need to restrict the exhaust outlets more, sometimes they almost block one outlet completely. The engines are sensitive to needing more muffler pressure going to the fuel tank. If you get good muffler pressure and don't try to use the larger props, the engines then tend to work well in any position on the airplane. When some folks remove the internal muffler baffles on the stock muffler, they start running into fuel draw problems too. A few folks have replaced the carbs on their engines with carbs that had a smaller venturi and that helped too.