Michaux is a great place to ride! Check out this thread:
Not on your list is Green Ridge State Forest. I've done quite a bit of that on my '69 Guzzi Ambassador on street tires.
The Frederick Municipal Forest (commonly know as the "Frederick watershed") is a small, but fun area to ride as well.
Buchanan and Tuscarora State Forests, plus the numerous State Game Lands in PA have some interesting riding too. Bark Rd. and Oregon Rd. in SGL 65 are two of my favorites. http://goo.gl/maps/AW9jw
Lots more to explore in that area.