Thinking about container weight.

Today I started filling containers for the roof to get an idea of how much I’m going to need of various materials. Experimenting with different mixes, comparing weights, and thinking about options. A couple weeks ago I bought a cubic yard of GaiaSoil and am now experimenting with that. The guy from Gaia Institute recommended using six inches of their mix (which is made of a mixture of crumbled styrofoam and compost), a layer of coir-fiber cloth, and then another few inches of compost on top. So that’s more or less what I’m doing, around six inches of each growing medium, plus a couple of inches of drainage rocks. When I was weighing things I realized that much rock weighs about 10 lbs. What if all or part of that was replaced with loose fill packing peanuts? Would the container be too light for the roof? Wow what a concept.