I would mount sideways. Fits fine and you don't run into the problems running inverted involves. Just make sure you have adequate cooling. Remember, exit area should be at least 3 times entry area. Also, with the shape of the cowling I don't think upright or inverted will look very good. If you want, you can get a slightly deeper cowl from Stans Fibertech that will allow the mounting of a Pitts style muffler.