I don't know about Jumbomax, but I do use 1/8 oversize Winn, and I couldn't go back to a skinny grip. As to the bit about release, if you're going to release first you have to cock. I find a standard grip makes me hold the club too tightly to cock the wrists, and if you don't cock them you can't release them. The oversize feels more secure, so I relax my grip and I get a better wrist cock. I now hold the club so loosely with my right hand that I can take it back well past parallel; not bad for an arthritic 63 year old.
