I too used carriage bolts with nuts that have the lining to keep them from loosening. I also cut a 1x3 oak stock pieces for extra strength inside where the washer and bolt were put. The wood gives it a better look, and also allows for a more snug fit (the wood wall in the camper is paper thin). I did both the front and the back ... although the back was the only ones that were vibrating out while traveling. It appears to be a common problem. NOt sure why the dealer says otherwise.
Also fixed my indoor speaker setup. DearTruc was correct. It was wired inside in a way I don't understand. I now have stereo inside that works with the DVD system. I am also going to buy a small subwoofer ... as there are indeed wires for that that wern't being used.
Thanks everyone for comments, pictures, suggestions. This is a great forum!