I have a Casseroll that was built up in 2009. I took it for an overnight trip with ~30lbs on a rear rack with ~5lbs in a front rack bag. What I found was that any time I stood up, there was significant shimmying sideways (rigid body). I should qualify this by saying that it might be the rear rack that contributed the most to this, as it was an inexpensive aluminium rack and not something like a Tubus Cargo, which is pretty stiff and sturdy.