I have a straight on single angle of a Tusk rehearsal from '79. But the quality's pretty awful as well. The sound is decent, but the video is pretty bad. You can barely make out the band.
It's funny though, because they play "Not That Funny" then go into Rhiannon and the power goes out or something. Stevie starts laughing because it was her song that had the bad luck and she says "It's not that FUNNY is it..."
Also funny because when they're playing "I KNow I'm Not Wrong" Lindsey's doing his 'buh-buh-buh-buh's and he gets angry and screams "STEVIE!" to get her to do back-up. She kinda then gets this look like 'Huh? Oh crap, that's right!' and rushes to the mic, then she's mad at Lindsey for yelling at her. Funny moment.
....that doesn't answer your question, haha, sorry.
But I figured I'd share. If anyone has that documentary, I'd love to trade or purchase it from you too!