For most tricks that don't include a rotation, my back foot is dead center of the tail, maybe a little offset to the heelside and slightly back, but definitely right in the "meat". Any spins or shuv-it tricks, I adjust for the scoop accordingly.
I might have a more central placement due to skating mostly transition
I was going to ask, because as I've refined tricks I'd say I more like I hover towards center but favor different pressure points depending. Like w kickflips I'm slightly in the pocket just barely, with the ball of my foot and my toes just over the midline but generally favoring the heel side slightly in terms of pressure distribution. It makes them feel kind of effortless.