Wanting input as to lumber movement and possible problems.  Imagine a solid lumber ash horizontal ( with an arc in it) piece about 5′ in length with another solid piece of ash ,horizontal,same length below.  Sandwiched between the two are solid lumber pieces ( 2″ wide-21″length) slats on each side of a solid lumber panel in the center of the headboard.  Panel is 35″ wide and +/- 24″ in height (with the arc in the center of the panel).  Wanting to know how to fasten the slats ( I was thinking bisquits) and the panel ( bisq. or mort.-tenon)  Wondering about expansion/contraction,primarily on the panel.  More info for you guys if needed to answer the question.  Thanks—WW57