Hi Algae!
I have switched over to 100% akadama for my deciduous trees and 1-1-1 pumice-lava-akadama for my pines. I constructed a greenhouse this winter and bought a heating device which has kept the greenhouse at around 2 degrees celsius all winter. It has also kept the rain and snow at bay. The greenhouse and the heating device has elimnated all the problems of the akadama and so far the trees are healthy and the akadama seems to hold its shape.