ORIGINAL: ChuckW
I'd look for a grommet for another mini or micro servo and modify the mounting tab on the HS-55 to accept it. Shouldn't be very difficult to do.
I will do that if necessary, but first I'd like to try to use a silicon or simlar sealer underneath the mount tab if that is at all possible, just something to give it some cushion. I am afraid to try to enlarge the hole for a grommet and perhaps weaken the tab.