Mike Higgens sent this link: http://www.emhart.com/products/pop/lsh.htm

It is for rivets that actually have 'washers' (for lack of a better description) attached to the end and they offer a much larger crush area on the back side of the surface! I like the idea of flipping the boat over and filling the current holes, then redrilling and then giving these rivets a shot!

I looked a the holes again and I have the same problems--the ends are loose and the centers are nice and tight. the rear ones have screws in them, so I'm wondering happened?!