The first way I tried attaching the 650 tank dampers to the front of the frame was with a 1/4" bolt through the neck gussets using washers to clamp the dampers against the gussets. I had seen pix of this method either on this site or XS-650 Garage. I found that this allowed the tank to rock slightly side-to-side, and it just didn't seem to be the best way to transfer the tank weight back into the frame.
Being naturally cheap, I bought a couple of 3/4" copper pipe end caps, drilled 1/4" holes centered in their ends and shortened them with a tubing cutter to sit flush in the pockets in the dampers. I had to enlarge the pocket diameter a bit so the caps would slip in without distorting the outside diameter of the dampers - just wrap some coarse sandpaper (60 grit) around a socket that nearly fits the pocket and twist. Takes awhile, but eventually enough rubber abrades evenly around the ID to get the pipe cap in. Very solid now.
Being naturally cheap, I bought a couple of 3/4" copper pipe end caps, drilled 1/4" holes centered in their ends and shortened them with a tubing cutter to sit flush in the pockets in the dampers. I had to enlarge the pocket diameter a bit so the caps would slip in without distorting the outside diameter of the dampers - just wrap some coarse sandpaper (60 grit) around a socket that nearly fits the pocket and twist. Takes awhile, but eventually enough rubber abrades evenly around the ID to get the pipe cap in. Very solid now.