Here is a shot of the micro stop counter sink tool and pneumatic rivet squeezer. I have a bit of aluminum metal work experience and already had these tools, or I would have NOT attempted to do the pads like it did. I countersink the hole in the bottom of the pads to accept the rivet flush.
The micro stop is fine threaded and allows adjustment so you can get a perfect depth on the countersink to fit the rivet head. I left them a bit high because I didn't want any extra rivet on the inside to get in the way of the tumblers. And, the little channel parts are so small and the hole clearance is way less than it should be so setting the rivet to standards can split or crack the part. I could have used a soft rivet here but had a bunch of standard.
Here is the rivet squeezer, really handy of you have a lot of rivets to squeeze.
Closeup of the dirt side of one of the pads with the rivet set.
Jim