In the new release I added a module setting in EventCalendar for "Pad Empty Days" which defaults to true. When this is true, some br elements are included on the empty days which makes the calendar expand and look better when its in the center pane. If you set it to false the calendar will render more compactly. You may still need to make your right column a little wider to fit it nicely, or you may be able to make it even more compact if you tweak the mpdatacalendar.css file in your skin.
Click the gears icon next to the title of the module to get to the module setings.
Hope it helps,