I used 1/4" pop rivets made of Monel.
I have read in a thread several years ago that Amel used rivets as a precaution against damaging the foil. The rivets would break rather than the foil if something prevented the foil from turning. I guess if they started putting bolts instead, they decided it wasn't much of a risk. I don't see a need for bolts, and the rivets give me some sense of security, even if it is misplaced.