Great thank you for the reply and the effort you put into your videos.
I do know some industrial foaming folks use pure nitrogen vs air for their foam creation due it being inert and if you've ever had Guiness, you know the foam is different. (much smaller bubbles). it might be a fun experiment since i have some nitrogen tanks from brewing so I'd just need to rig up some duct tape manifold on my compressor. I really am curious about the lower limit of density. I'll try some experiments and contribute my findings.
I have a specialty mushroom farm and my mycelium blocks when totally tried out are super light and make great insulation. I think I might build some blocks with really dried out versions as the core with air crete around them thick enough to have some strength.