I just checked my 1 year old Ohana concert and it has similar, although slightly, less dips in the top on either side of the bridge. I also noticed that the thickness of the sound box drops off slightly at the bottom inch or so. This appears to be by design as it is even all the way across. I do not have any rotation of the bridge mount. I live 2 miles from the beach and I'm too cheap for air-conditioning so humidity is not a big issue for me.