I think this is going to be very helpful for me. I'm going to edit it into progressive slowmo. I hope I'm not just kidding myself, but I think I can learn to do this serve the way the guy in the video does it. The serve in the vid is much better, in certain important respects (ie., my current second serve is much faster than the twist serve in the vid, but I double fault too much, and the serve in the vid would solve that problem -- plus, at my level, that twist serve poses some unique problems for most returners), than my current second serve, which is basically just a slice first serve.
Thanks for posting this.