Some say that just like classical guitar, thumb on the back of the neck is supposed to be the 'proper' way to play. I'd really like to know why. I can play for maybe five minutes like this before my hand cramps up. So just like guitar, I hang my thumb over so I can play comfortably for more than a few minutes. On guitar I actually thumb 6/1 to do F Major too. I really only put my thumb behind to do barre chords. For those who do strict thumb on back, was it simply a matter of building the right muscle group over time? I've given up trying it on acoustic guitar (arthritis), but since uke is lighter strung, and I've only been playing for a year, I wonder if I should suffer and try to habituate with 'proper' technique. I found this video of The Ohtas playing together. Sr , being a trained jazz musician keeps thumb behind the whole time. Jr. however has thumb over.