The cut-off point between having white space or not, is not good. If only they could control when to make the switch.
Experimenting a little, if you reduce the side-to-side size of the window even more, the side bar with our info takes up the entire window. It leaves me to think that might be the reason for white space generation. Maybe if they locked-down the size of the member side bar, that just might stop the crazy phenomena.