RE: RCG 15 CC Cylinder rotation
Yes there is a difference in the ports between the 15 beam and cross mount. The 15 beam has three ports while the 15 cross only has two. This is one of the reasons that the 15 beam makes more power. The ports in the cylinders match ports cast into the crank case.
The best choice to rotate the cylinder would be the beam mount, but it will require internal machining of the crankcase. If you ask me not worth the effort