The Post Canyon Recreation Area is a multi-use trail network formed of Hood River County property and a patchwork of State Park, USDA Forest Service, and private land. The area is also an ongoing tree farm operation, so be aware of potential closures. Expect traffic in both directions and yield to hikers and equestrian riders.
Grand Prix (158) is a great follow up to Bad Motor Scooter (158), there's plenty of fast flow and options to pump, fitted between a consecutive series of berms as the trail winds back and forth across a forested slope.
It's easy to pick up plenty of speed on the straightaways but the shallow nature of many of the berms means riders may need some heavy braking to make it around.