Does anyone else have a problem with their tubes getting crooked and almost falling out when the move it from home to gig and back? Mine always seem to get knocked about (LSC, 23" Head) since there is not much room at all in the back. I think the power chord knocks them about. Anyway, does anyone have tube spring retainers installed? Is it tough to do and where can I find them? I've looked all over online and can't find any.