Center simulation on update

Hi guys, I'm having a graph with 50 nodes and connections, I rad the open issue about adding 'alpha' to the 'simulationOptios', the problem I am having is : how I can center the simulation to the center of 'ZoomSvg' and specifically the center of the 'rect' html element that is added under hood.

I want to set the rect x and y attributes. 

Is there any way doing that?? 