Planarization

So... I know there`s many tutorials... but it seems that any worked at this !@$! surface! it never gets all panel planar.. and, believe me, I tried !

I did the Daniel Piker`s definition and with no success, When I change the strength of the planar forces it gets crazy as seen at the second image.

I have tried other 2 definitions but none worked, it must be me.. anyway, if someone could give me a hint that would be great !