got it got it got it.i'll take a mirror with me so i get the right size rivnut.your the goods jeff.right on brother.
Coat the screws with antisieze before attaching the mirror. This will prevent corrosion and make them easier to remove should the need arise.
You can also buy an individual tool to install these. It works kind of on the same principle of the nut and bolt like Jeff posted (thanks, good info!). It is a collar that you run the bolt through... if memory serves right, it is serrated at the bottom ... It was a long time ago, but I think it was $5 at Ace Hardware. You just have to know what screw thread size you need.
Did a quick search and found this instead ... http://www.ridgelineownersclub.com/forums/showthread.php?t=10746
I posted the factory installation instruction for the sport mirrors in the tech article section. See if this link works ... http://mmb.maverick.to/showthread.php?t=53142 Bob
How about taking off you interior door panel, lower the window and just put a bolt throught he mirror and put a nut on the inside?