In my 2008 Odyssey 482, there is a panel about 9" x 18" screwed in place in the adjacent wardrobe, I assume the plumbing is behind there ? However I'm sure you would have noticed it.
I have a problem with mine, it is only 2 weeks old and been subject to about 10 showers and where the circular bowl meets the vertical sides a crack in the plastic weld has started. It is in the hands of the dealer to sort but I am not happy. It seems the base is not supported well enough underneith. Anyone else out there seen this? Chris