Re: How to better play thumb barre chords a la Hendrix?
I agree with a lit of the above here. I too have smaller hands, and Hendrix chords, a LOT of Mayer stuff and even simple SRV rhythms cause me a lot of issues. Even simple stuff like the Cold Shot rhythm I couldn't do like the guy from Texas Blues Alley showed. I can only do it on very specific guitars with:
- narrow profile. 1 5/8 nut at the most, though I don't think anything makes anything smaller
- round fretboards. Small but important difference, and allows your thumb to wrap more easily.
- for me, asymmetrical necks works the best. I can do most stuff on my Peavey Wolfgang. My ideal neck would be the Musicman Axis because the scooped lower side allows for a tiny bit more grip
- in terms of profile, I prefer rounder vs V. There's somewhere to rest you fingers on a C, vs a V. If you have smaller than average palms a V may work better.
The one thing I found helped me a lot is 'pushing' my palm into the back of the neck. Sounds obvious but I was surprised at how much room I had because I would reach and bar with my fingers, rather than giving me that extension with a push. I think it was habitual because when you play classical or solo, you usually anchor with your thumb on the back and try to keep your fingers and palm as free as possible.
Hope that helps!