The last and most important point of contact is the pad and base of the index and thumb pad unless you have some kind of crazy g.i. joe kung fu claw grip on the disc. The further away/out that point of contact/pivot is, the more leverage you can get on the disc. When the disc is too deep into the base of palm it's harder to maintain the thumb leverage against the index/pivot point and the other fingers tend to resist the pivot more than aid it. I still have the rear of the disc in the "butt cheeks" of the palm but not as deep and only for a sec when I'm gripping hard with the thumb in the power zone. You should be able to control/spring the disc without the thumb on the disc just using your fingers.