If I had a good milling machine I would start by milling the crankcase to about 1/2 way and make a 3 piece case. The new back half would incorperate a better way to mount engine and at the same time give a person a chance to rework the passage ways in the bottom for best performance. I am with Pe Reivers on not trying to stuff the case to much if it does not help in our RPM range. Capt,n