According to the DMG, page 303:
For 200 pounds of an item's weight, it deals 1d6 damage, as long as it falls at least 10 feet. The distance also comes into play, adding 1d6 additional damage for each 10-foot increment falling beyond the first (up to a maximum of 20d6 points of damage).
I read that it meant that the damage added by the distance of the hats dropped to 20d6, but that the damage based on the weight of the object had no hat.
One of my friends said that it remembers a lot of talk about the subject years ago and a decision that the damage caused by the fall of an object has a strict ceiling of 20d6, regardless extra weight.
Unfortunately, he can not find where the things he remembers have been told, and all we need to go on is the text of the book. Does anyone know what is the correct answer? Preferably with a source?