Tim,

Have you tried fitting one of the Mac25 cylinders to the BME case? I tried fitting a cylinder to a case and found that the mounting lugs line up after rotating the cylinder a few degrees. This would mean that the exhaust would not be exactly perpendicular to the crankshaft centerline. A custom exhaust header would probably need to be created. As long as the relationship between the ports, case, and piston skirt remain the same it might work. Unfortunately I don't have the equipment or skills to cut / weld a crankshaft or I'd try it myself.