To be clear, the ball in question is not part of a pin stack. It is there all by itself to mess with the rotation of the plug. The hole in the plug for the ball (which must be smaller in diameter than the ball) does not need to be drilled all the way through to the keyway, ideally it would not. The one I made used the empty #6 pin because it was easier to build that way.
If anyone wants to recreate it, detent balls and springs can be had from
http://www.brownells.com/gunsmith-tools-supplies/handgun-tools/crane-tools/crane-ball-spring-kit-sku713035000-9849-25596.aspx?sku=713035000 for $18 + shipping. Take out the plug and drill (after making sure the follower is pulled clear so it won't be drilled also) a hole though the 6th pin hole in the cylinder with a #30 drill bit. Then tap about half of that hole (OK to counter-bore to a large OD if that matches up to a tap you have). Reinstall the plug, drop the ball in, drop the spring (the spring that came with the detent kit) in, then put in a set screw. If there is not much resistance to tension then use a longer set screw etc.
It does not impart a constant friction. Rather it sets up a good deal of friction (such that no pins will bind because the plug has not rotated enough) and then as the ball is pushed up via plug rotation the friction drops, but when it drops the pins are already bound up. Trying to establish the right tension for picking (or bumping) in the midst of that caming action would take a lot of skill. Probably not a barrier for impressioning.
For what it is worth, it could be adapted to basically any lock that one would manipulate after applying radial tension to something (lever, disc, tubular, etc.)
