"Having studied this a bit, and checking with a few engineers, ( not counting being one ) I can see no merit whatever in a flat piston over the conical cup **properly adjusted** "
I know a few engineers and most tend to over analyze and rely on theory rather than experience. There is no replacement for experience when working with airguns. Flat top pistons do provide more power per stroke than the conical pistons. There is more to it than sealing and adjusting. Try it before you condemn it.