My bumpy srfgrid

I need to create a surface from 25 poin

ts (16 in the outer ellipse, 8 in the inner ellipse and a center) and to do so i use the SrfGrid component (with u=5). However, on the top and the bottom of the ellipses i get this very odd dent/bump that messes up my results.

The way i retrieve the points are a bit lenghty, so fee

l free to ignore that part. Can anyone help me how to get a nice quadratic curved bubble out of these points or does anyone have a better method to do so?

Kind regards,

Jeroen