Cindy did the KT52 tuned by Ken Turner, some say that was best tuned 52 going.
It had a reduced cylinder, was short stroked and had a lightweight alloy piston running on bearings, all that was in 1988!
Here is an article about it from an 1988 Airgunner magazine:
https://www.dropbox.com/s/4gnkfo8rzfwblkq/KT52.PDF?dl=0