Hello Ted,
I don't have a lath so I didn't shave the bottom of the cylinder. They have great compression any way. When you pull the cylinder and put the piston at the bottom of the stroke it is obvious that the skirt is blocking the transfer. Major modifications can decrease performance. All of the related variables must be considered. The cylinder doesn't have much meat around the ports to allow enlargement. Here is a picture of the piston at BDC.

Dave