I tend to anchor my thumb wherever seems most comfortable for the attack and tone I'm going for. I play Precisions, and I usually anchor on the pickup when I'm playing on the E string, and anchor on the E string when I'm playing on the A, D, or G.
However, these days I find myself often favoring more fret clang, so I'll anchor on the top of the fretboard at times.
However, these days I find myself often favoring more fret clang, so I'll anchor on the top of the fretboard at times.