I have the 66 inch extra and have a TT 91 on it and the stock muffler fits nicely inside the cowl. I have it angled down and to the left side of the plane and it exits out the bottom of the cowl. I am not sure how the saito exhaust pipe angles out of the head. You can turn the engine mount and mount it inverted. The cowl will look much better with the engine mounted this way. This plane is awsome it is the best flying plane I have ever flown and the TT 91 hauls it around nicely.

Rick