Thanks for the clear photos. Vibration suppression comes up in some of my projects/experiments, and there have been times that I went to great lengths to control it. Sorbothane 'T' washers, along with matching 'O' Sorbothane washers did the trick for me, but I do appreciate ideas of this nature as well. One consideration is the torque or tightness of the attaching bolt or screw, so as not to 'squish' all the goodness (load rating) of the washer being used.