The problem is that you are going to experience a tougher fuel draw when inverted, and your "setting" is going to change. You want to establish even running in all attitudes.

IDEALY, the centerline that runs horizontally through the center of your tank, should be located 1/4" to 3/8" below the spraybar in the engine.

IE > If your tank is 4" high, then the centerline is at 2" from the bottom. Take something like a black SHARPIE marker, and draw a line horizontally through the tank. Now mount the tank with that line 1/4" to 3/8" below the spraybar.