Surface Manipulation / Multiple Effectors

I am trying to manipulate a surface to bulge at areas where certain points are present. The bulge height/affector area is also controlled based on distance to each specific point. 

I can achieve this with one attractor, and can get it to work with a variation of Michael Pryor's repel/attract example with multiple attractors - however the effect is not as pronounced as my first solution which gets a tighter bulge but results in multiple surfaces.

Solutions in the forum have come close to what I am trying to achieve,  and I am sure it is probably a minor modification to the script/tree structure, but any advice would be appreciated.