I'm in the process of refinishing a 13' Scamp
that had an awning
rail bolted on.
Virtually every bolt leaked and marred the ensolite.
I have installed 4 or 5 rails over the last few years and NONE are loose or leaking. The first awning
rail was in 2006 and was on an 87 16" Scamp
that I gave to my son and grand kids.
It was installed with aluminum rivets and butyl tape.
To this day it's tight, leak free and the rivets do not show on the interior.
If you use 3/16 X1/4 pop rivets and butyl tape you will have no problems.
Use a drill stop collar on your drill to ensure you will not penetrate the ensolite.