I've got the same problem! We had a big branch break off one of the trees a couple of months ago during a bad wind storm. Bailey was just sure that it would fit through the doggie door so that she could make mulch for me! The doggie door is big, but not THAT big! We're still trying to figure out how she dragged the branch up to the house! She's a tiny little thing and only weighs 50 pounds. The branch weighed at least 25!
Everyone tells us that Labs start to calm down by the time they are 2. She'll be 2 in October, and I can't wait.