My apex is typically lower than most. On my short boards, between 2.25 and 2.75 inches thick, my apex, the red dot, will run in the mid .65 to low .6 range. It will creep up as the boards get thicker.
The apex is the lower middle Z number. You have to add or subtract the bottom contour. In this case it’s -.04. So the apex is at .65 minus .04 that makes your apex at 6.1 which is on the lower side.
When an apex dips much below this .6 mark, it will work but the rider has to be very sensitive to the lower edge, which if taken too far, is likely to catch, hang up and push back on turns.
Below is a typical rail from most shapers. .84 less the .04 equals .8. That gives it the, as we call it, the Frisbee rail feel, which is incredibly popular these days and has been for decades. It’s safe. No catch. It feels “loose.” But there is always a flip side: it’s not as sensitive, slower to set, and a release that is a little slower as well.
Hope this helps.