SpaceX on Twitter said:Falcon 9 rocket back at port https://instagram.com/p/BEFyQh0F8eB/
So, they recovered it without it tipping over in the rough seas. Maybe our concerns weren't warranted after all. Maybe the CG is low enough to where it'd take an excessive tilt to tip the rocket over.
Now we have to see if the rocket works - if the landing didn't impart damage.