Good information there.

Ok, one last shot at why vertical is better (don't take this too seriously, ok?)

If the forces are at an angle, and we all agree that balsa failes more easily along the grain than cross-grain, then any failure in the web should show up at a grain-wise crack. If the web is veritcal, the crack has little effect, since both ends are still glued to the spars. If the web is horizontal, even a small crack disconnects the top and bottom spars

I'm only talking about cases where the sw is individual sheets between the ribs, not the one long sheet between the spars.