Overhand is the way to go. After warm ups and stretching / shakes, start from the base and make sure to grab the base (lightly) with your other hand soon as you reach the top. I think when I was in the early stages of PE I was using wrong techniques, probably doing underhand with the thumb on top (seems intuitive to do overhand but sometimes common sense isn't always common as in my case). So basically by doing it wrong the top part looks and is thicker than the bottom, but with a healthy overhand it should even it out, or at least be more conducive then otherwise.

So used to the overhand grip now that my hands are practically in the permanent ok grip position hahaha!