I did 20 minutes without my center paper cutout and managed to dig a tiny zone in the center. Yaaaaay. Then I spent two hours ignoring it and trying to get the outside zone down.

On the plus side that outer zone at 70%+ diameter looks spherical now.

Now I have a choice: I think I'm close to a parabola. With that deeper center, if I can flatten the inner edge of that transition I'm very close. Do I keep going all the way to a completely flat sphere, or try to stop halfway through and thread the tricky needle?