To me, the most important point is not even where Jerry himself played most or some of the time, it's that changing your picking position very much changes your tone.
I guess I might be alone in thinking that this was a no-brainer, but that notion seems a little surreal. I find it hard to believe that there are even first-year guitar students who don't understand this concept.
I grew up listening to the Grateful Dead's music and possessing the notion that playing like Jer was simply out of my reach. So, like a lot of other kids, I played loud, heavy music instead. I know now that I was only compensating for very bad tone. Later I played country music in bars for a few years, and after getting the feel for country, suddenly Jerry style became realistic for me. Tone came later...
My point is, varying your pick attack and position is absolutely crucial to your tone. More so with very clean tone. I was forced to learn this way before I tried to emulate Jerry. If there was an overall "sweet spot" for picking, I'm sure we would have analyzed the living shit out of it by now anyway.