Instead of silicone, I was thinking of using a strip of butyl rubber alongside the foam. That's what lots of people use in the marine world to bed deck hardware. Downside is that it's pretty sticky, so I wouldn't be able to adjust the canopy placement once it's in place. But I might be able...
have a fiberglass canopy on my 96 f-150, and I'm preparing to outfit the inside for camping. But first, I need to reseat the canopy, because water weeps through the seam between the canopy and bed along the sides in a few spots. Canopy is bolted to bed - three bolts each side.
As I recall, I...