Sounds like an awful nice area you've got there. I like your idea of "shooting Lanes", but in my opinion 30 yards wide is a bit too much of an opening. I'd look at around 30' (10 yards, perhaps). On a somewhat smaller scale we did a similar thing on some property here in Tn and found it gave us two advantages. First was the openings for easier sighting/shooting and second was the fact that by cutting the high grasses out, new green growth came up and the deer loved it.