Missing screws on side sills

[Qualitywires.com]

if you look in the section on how to fix things on this site..it gives a pretty good description on how to fix.
http://www.viperclub.org/menus/index_how_illup.htm

I would thing the rivet idea would work on the bottom too.

 

[GTS Dean]

A simple fix is to use a small hammer and/or punch to peen the holes back flat. Before you reinstall the screws, dab them into the end of a tube of silicone, then install and snug them up. Even if they don't torque like they should, they will bond everything together well enough to not lose the fasteners until you take them off again.