Back in the day when we were flying ST G-15 glow's in CL Goodyear racers, the oil thinking went like this. Too little oil and the bottom end of the conrod blows. Too much oil and the ball bearings hydroplane rather than rolling, and one or both bearings blow. So, according to this thinking, too much oil in a ball bearing engine is not good. However, other than the race situation mentioned above, I don't recall ever blowing a bearing, too much oil or not.