google maps api v3 + infoBubble in markerClusterer

I was trying to add an infoBubble to a markerCluster in the 'clusterclick' event but the infoBubble.Open method ask for a 'marker' parameter to bind with. The problem is that a markerCluster is not a google.maps.Point so it's not posible to bind the infoBubble to it.

I assigned the possition of the markerCluster to the infoBubble but the infoBubble redraws in the new position moving the marker from its possition.

Has anyone had the same problem? Is there a solution without modifing the original infoBubble code?

http://google-maps-utility-library-v3.googlecode.com/svn/trunk/infobubble/