Exploring the *back* half of the neck
 

I started out playing a lot of thumb over bass F chord and thumb over bass D7 chord blues songs, but recently for fingerstyle am discovering the joy of that untraveled back half of the neck for thumb position.

Going back behind the center of the neck with the thumb places the fingers even more vertically, making it even easier to fret the strings and sound chords cleanly and it seems to put less stress on my elbow.

Only recently that I ever tried this much less find success with it. Anyone else?

Thumb behind the neck is standard for most people though using various thumb positions is fine also. Watch some classical guitar youtubes to see what those guitarists normally do when playing.

I find myself on very rare occasions playing that thumb-wrap F, but not a lot. I like to float my hand, particularly when playing single note runs between chords. Often my thumb isn't actually touching the neck at all, I am floating my left hand. For some chords my thumb finds itself on the middle of the back, but when I am running down II-V's (Cm7 - F9 at the 8th fret, for example) my thumb is stuck up in the air and I am anchoring at the fleshy base of my index finger. The key is to free up and relax your fingers, since they are doing the work and your thumb is just along as a supporting act...

You just discovered what all classical players are taught on the first day. ;) (To be fair, it matters more for classical because the neck is wider.)