Is there a way to have the widget size update with the cart size as well? This would also need anything below it to get pushed down as well though.
So another approach - see what You think... EcwidDemo_JHSv2.hype.zip (21.0 KB)
My experience was everything in the "960px" layout was larger than it needed to be anyway, so I made a change to that layout: the widget is now 700 pixels wide (instead of 960 px). The breakpoint is still the same. Page height & widget height have not changed.
One more adjustment - I selected the "Zoom contents"checkbox ("Metrics Inspector" > "Flexible Layout" area - just below the "Scale Behavior" menu).
The "600px" layout has this same checkbox selected - at these smaller sizes the "Zoom contents" settings makes things a bit smoother when adjusting the page size.