I am a righty and I have the tendency to leave the thumb on the bottom hand straight down the shaft with a bit of presure. I see most say it needs to wrap around. Would this cause any major problems with my game? Thanks as always
placing the thumb on top of the shaft gives your right hand too much control over the club. Essentially what i mean by this is that it will make you very prone to casting the club from the top of your swing leading to... well just about anything, drop kicks, thin contact, pulls or slices depending upon how the rest of your swing moves.
I say 100% TAKE THAT THUMB OFF THE CLUB!
I wouldnt call it "wrapping" the thumb, that, for anyone reading may come across almost as holding the club in a fist... I say you 'take it off the club' by moving the pad of the thumb off of the grip and positioning the thumb across the shaft so that just the inside half of the knuckle lightly touches the upper target-side quarter of the grip. it will feel like much less control over the club, essentially making this change will alow only very small adjustments to be made with the hands and put most control of the club into the larger muscles of your body.