Here is a motionbased page with what is basically rideable at West Point Dam. You can also get directions from the motionbased page. http://trail.motionbased.com/trail/activity/5040067
There is a little lag in the mileage as I stopped to remove a fallen branch and forgot to restart the Garmin. The start shown is not the official trailhead but it gives the best start location for the out and back that the trail currently is. When do you think you'll be checking it out? I may be able to guide you since nothing is marked yet and a couple spots may be iffy to navigate. I am also doing the Wheels O' Fire. Also keep in mind the first 2.4 miles is focused on beginner and advanced beginner and is basically finished, the rest is mostly rake-n-ride single track with no tread work done yet. The most you have to watch for is a few dips may be a little more abrupt than they appear.
There is also Pyne Road Park http://trail.motionbased.com/trail/activity/1896816
closer to LaGrange. Doing that trail one way then the opposite can give you between 7-8 miles. The route shown cuts it a little shorter than that. Since last fall more and more equestrians have come to these trails as they were kicked out of the other side of the park so there is some piles to go around or bunny hop. This trail is five minutes from my house so it is usually the one I go to the most. That is until West Point is finished.