I have the Revelate Pika which claims to need only 6.5" of clearance. I used it on a brevet once and didn't like how inaccessible everything was. Seemed like no matter what I wanted it was at the bottom of the bag. Whatever speed advantage I may have gained from dropping the weight of the rack I lost many times over digging around for stuff in the bag at controls. Other than that it's a nice bag. I use it a lot, just not on brevets.