Wayne Parham Messages: 18787 Registered: January 2001
Illuminati (33rd Degree)
I've had good experience with closed cell foam. It expands to fill in the area and preloads the panels. Forms a solid mass and doesn't weigh much at all. The one downside is it's easy to overfill, which then can over expand and burst panels. So you have to be careful to consider the expansion when using the stuff, and don't fill the area, let the expansion fill the space.