Yes , I have the same problem. When I start going it goes right away-does yours? I will probably not do anything with mine - it is not worth me taking the rear bulkhead out to fix. If I did I would put some kind of warp in it that you wouldn't notice. The drag race guys run all their pannels in one of those bead making things. My issue is simple "
oil canning" The guys with carpet probably do not have the problem but then their cars are alot heavier and slower.