I decided to add a couple of additional supports to the internal frame. I inadvertently mounted the inner frame with the slats running in the same direction as the slats on the bottom deck. For optimum strength and support it would have been better to run the slats in opposite directions so that they criss-cross over each other as often as possible. Think of the crosswise grain of plywood and the amazing strenght to thickness ratio that has.
Adding the additional supports will make up for the difference at the cost of a negligible amount of additional weight.
