Sean, if Mosconi used a slip stroke "often," say what 30%, 20% of the time, where is the video of him using it? There's at least several hours of Mosconi on tape -- should be plenty, no?
Lou Figueroa
Lou, when one looks at the video footage available (sadly there isn't enough of Mosconi, I could watch him all day), the problem is that the camera centers the table in the view -- as most pool footage does -- and the player's body is clipped from the view. Especially that grip hand. And, if you're looking for something "subtle" like a grip hand readjustment -- combined with the rare occurrence when that grip hand is in view -- it makes it even harder.
Having said all that, though, I maintain that I see Willie use a small slip stroke on some of the shots (the ones that Danny / Sloppy Pockets mentions).
The key here, is that Willie didn't use it on every shot. The fact that he uses a pinned grip hand much of the time on those short punchy shots, and sprinkles in a slip stroke "here and there," doesn't make it easy to convince folks like you and Dale, who, respectfully, I think are missing the importance of *when* Willie is doing that slight readjustment. The cue is already traveling backwards when that readjustment is made, and that's slip stroke territory.
It's not a terrible thing that Willie had this terrific technique in his toolbox. In fact, it's glorious.
-Sean