On the piston I windowed it & dropped the boysen port before the replate. On a kx500 it equals 2.5 hp in the mid range. The reason I think it works like that is if you think of swinging a bucket to keep the water in the bottom the highest point of pressure is in the very bottom so a window relieves this hgih pressure point.
The piston is also skirt coated with an antifriction coating & ceramic on top
Here's the boysen port drop