Not to highjack the thread.....To those with rack cases....I just moved my Hartke HA3500 to a SKB Rolling Rack. I'm glad that I racked the head to protect it (and save my back). However, I'm a little concerned that the rack case feels a bit "slippery" while setting on top of my 4x10 cab. I'm afraid that playing at any appreciable volume may cause the case to slip from the cab. I haven't played out with it yet (couple of weeks until my next gig). Are my fears realistic? Should I worry about the case vibrating off? It isn't like I'm playing at full volume, it's just that the case seems to move about pretty easily.