Not sure about UA, but was just at the airport to help send my parents-in-law back to India. They were flying DL (connecting to AF, but that is probably irrelevant). They put the bag on the scale and the first one was 53 pounds - agent said it would have to be re-packed as policy allows comping just 2 pounds of extra weight from what is published - so 52 pounds. Long story shorter, the other three bags were either just over or just under the limit - re-packed, they had each of the 4 bags weighing exactly 52 in the end. I consider them very lucky to be able to meet the exception exactly to the limit without getting a hefty overweight fee.

Oh, and each of the bags got a heavy tag.