I kept the card thingy that came attached to my luggage ... it states on it the dimensions of the 29" suitcase, which total 61 1/2". I do not pack anything in the outer pockets (except the card thingy so that I can pull it out to show them if they question the size), and I don't unzip the extender. I was at first concerned about them measuring the handles, wheels etc, but I figure that as a consumer, I can only go by what the manufacturer says it is, and my tag says it's within their guidelines. I'm careful about the weight in it, but I don't like to take more suitcases than I need, so I love my 29".
doesn't take much to hit that 50lbs though. Coming home from WDW last trip I was at 49lbs.