Who would have thought a gravel road could be so difficult? There's only about 650 feet of climbing to the top of this loop, but it seems much longer than that. There's a couple of particularly steep sections on the climb that will wake you up. To add to the degree of difficulty, the road is covered with loose gravel and rocks.
Coming down the other side, (in the counter-clockwise direction shown), there are two short descents with >15% grade and the rocks are larger and looser than on the ascent. You'll have to pick your line carefully and keep your speed in control to stay on the bike.
The trail intersects with Pine Log Gap Road
near a bridge over Stamp Creek. There's a natural swimming hole here in case it is hot (there is some cover from the trees on the route, but not if the sun is directly overhead). There's also an impressive old iron furnace just to the northeast of this intersection. After that, it's an easy two miles back to the parking area on Stamp Creek Road.
Unfortunately it takes a PhD to understand when you can ride and how much it will cost. See Restrictions for trail closures during hunting season. As for the cost, from the odd government regulations category...
You'll need a hunting or fishing license to be present on the property (2017 annual $15/$100 resident/nonresident) whether or not it is hunting season and even if you're not hunting. (The property is owned by Aubrey Corporation; hunting rights are leased by the state).
If you have objections to buying a hunting/fishing license, you can purchase instead a "Lands Pass" (2017 annual $30/$60 res/nonres). The Lands Pass actually costs more because of the "loss of federal funds that come with hunting or fishing licenses".