Bolt Action latest FAQ under erratas for D-Day Overlord:
The Dug-in rules should be as follows:
Dug In gives you the benefits of being Down (-2 to be hit, halves HE hits), and if you issue a Down order, you double the benefits (-4 to be hit, quarters HE).
I think units in Trenches should just get Dug-in benefits, not hard cover ones as well.
