The longer the strings are, the longer the dampers have to be to effectively dampen.
The lowest tenor string is one of the longest strings in an upright. But the damper cannot be higher; it will hit the hammer. It cannot be lower, it will rub on the top bass string. (See in the photo above. Notice the chopped bottom of the damper block.)
Notice how Yamaha tries to deal with this problem by, 1, having the hammers edge higher so they can keep the damper longer and, 2, adding an over damper on the bottom tenor note.
