The grip on a K-super mag is high wrist. Just let your hand comform to the grip. Most of the bow's draw weight will come to rest in the web between your thumb and forefinger. That's what a high wrist is designed to do.
If you put too much pressure on the heel of your palm/grip, you'll be applying vertical torque to the bow. Likewise, if you squeeze the grip, you're likely to twist it out of alignment from side to side, creating side torque on the limbs.
If that's your picture under your handle, I'm surprised you can even shoot the super mag. It looks like you have a very long draw, in the 30-inch range. Drawn to that length the Supermag has to stack like all get out, and finger pinch has to be substantial, even with three under.