I noticed on the Fora .049, that they do not have a really large crank bore, but flare out the sides larger, so the fuel/air gets around the rod. Looks like about 20 degrees each side. They don't do the "turbo" cut like a lot of the car guys seem to like. I am guessing that this leaves the crankcase volume lower than opening up the whole crank bore. I noticed on an Axial motor that I have the the hole is bored off center, otherwise it would hit the crankpin. I like the Fora plan better.