R81's value is on target.
I've got the video below. It starts with the slug all of the way "out." I found that I could adjust the slug a bit more after the end of the video and when I did the picture looked a lot like it did in the beginning of the video.
http://www.youtube.com/watch?v=74tfWbkOgH0
Just out of curiosity, for those of us without super human horizontal frequency identification vision. Would measuring the frequency of the oscillator be something I could use a scope for? I don't have my probe yet so I couldn't do it now, but it sure seems like that'd be something I'd use it for in the future.