Overlapping nodes on hierarchical network graphs

First, thanks for all the time and effort to create and maintain networkD3! I was wondering if it would be possible to pass a parameter to add a "charge" to nodes to force more separation? (Apparently D3.js allows this.) If you look at the dendro or diagonal network examples on the home page, there is crowding and overlapping of the end nodes. I don't mind unlimited height or width. Also, there is a linkcolor parameter, could there also be a linksize or thickness parameter? Thanks!