1618 did rivets in the frame this year, 1/4" aluminum ones to match the kitbot. We ran them rivet-for-bolt, 72 in all, and had zero problems in testing and spirited running at Chesapeake. We had bumpers on three sides (the rear bumper was dropped after we realized how much of a pain in the butt it was to attach when we were already compliant), which seems to help by all indications.
Last year, we used 3/16" rivets to hold together the two members of our arm's tower. We used two on each side--you can see them on one side
here, just beside the radio antenna. Even with questionable mounting of our tower, particularly in the rear, the rivets held together fine through all of Palmetto and our off-season demonstrations. The rivets sheared on one side following a particularly nasty tip at Brunswick Eruption and would've been easily fixed had I not left the team's rivet tool 700 miles away in South Carolina.
(oops.) At that point, we just enlarged one hole to 1/4", stuck in a kitbot nut/bolt, and ran off to the next match.
Just two points of data--your mileage may vary, but I will note that rivets are the win.
