I just got talking to Bill. He said he does indeed do the line slip as you described, WJC. He got the idea in fact from some stuff by George Roberts. I should have caught on to what you were saying sooner because he showed me this earlier this summer. That's how I managed to shoot my whole line out of my rod. His description was worded different. He said "line slip" instead of "shooting line back" as he goes into the forward stroke. I still should have caught that.I guess there is not a lot of stuff out there by Roberts, at least that Bill has found, but he did find that valuable. He thinks it helps smooth out the backcast as well. He's kind of mixed a few styles. By the way, where you said WJC, "What I see is a huge improvement in the forward haul over the much nicer looking, smoother previous video when Bill was standing.", he said to say it's because of some tips from a veteran caster on the forum here. ( WJC, then imagine here a winking smiley he wanted me to put in that I guess we don't have.) He said Pocono was right about something too, but looking at his post isn't helpng me remeber what it was. Oh No! I'm having a senior moment here.
I also discussed the removal of a lot of body from the equation by kneeling. I don't think Bill thinks it hurts him that much but I think if he looked at the video of him standing and then kneeling and have them run side by side he may change his opinion on that.
As he said, he's still in the infancy of his distance casting. It's going to be interesting to see where this leads.