By the way, I also tested foxholes VS artillery. I used 105mm against a whole company of troops. The result was that - while not hiding - the difference between being in foxholes and being on open grass was so small that I could not be sure it was not statistical uncertainty. Troops would cower, but that seemed to provide almost no protection even when they were on top of foxholes.
However, when starting in hiding, losses were significantly smaller. I think at least cut by half - can't remember the exact numbers now.
I've been intending to run a series of tests on this sort of thing myself; troops in the open, troops in foxholes, troops in forest, troops in forest in foxholes, etc.