fiddlrgrrl said
@Fiddlerman I had watched your videos on positions awhile back. I just looked at them again and see that I had missed what I think was your main point.  Duh.

So, in every position, is your thumb right across from your first finger? Except of course, maybe 6th and higher -- and where do you hang on then, by the way?

Not exactly. From 4th position I use the curve of the neck for my thumb and keep it there for the upper positions as well.

For 1st, 2nd, and 3rd I'll keep my thumb against the neck curve by the peg box.

I also have not been trying to learn shifting by sliding -- I thought I was supposed to be able to just "hit it" through muscle and distance memory.  In practicing sliding, I realized that I leave my thumb behind an inch or more, which requires more stretching of my fingers than necessary.

One of my great teachers had us all practice slides to learn the shifting distance.

Keeping my thumb with my first finger requires some concentration, but I also see it adds to the feeling of stability. I took lessons for several months a couple of years ago, and I wish this had been mentioned.  All that was mentioned about the thumb was that I kept too much of it sticking up, but nothing about it in relation to the rest of the fingers.

I may make a new video.