We're floundering away from this topic...
Seriously, but in a lighthearted tone, I don't do LH fingering below the neck joint, that's RH slap and RH fiddle music fingering territory in the music I play. Sure, I'll goof around with thumb position in practice, but not seriously, my old hands and fingers wouldn't work well for that anyway. So my highest note is on the G string and is typically D although I'll occasionally reach down to E.
You do hear that concept expressed pretty often even by pro players in bluegrass and other roots DB circles -- some folks I've talked with don't even go higher than C. One even says if you want to go higher than C or D, get a cello.