I am making two screen doors out of Sapele for patio doors that are subject to serious rain--no overhang at back of house. The basic design is 1" x 3 1/2" styles and 3 1/2" rails, except that the lower part of the door contains a 5/16" x 12" panel, (edge-glued) bounded at the top by a 3 1/2" rail and at the bottom by an 8" wide rail. My question involves the joinery for the 8" rail. This is where my old screen doors have failed, although they admittedly lasted a long time. I'm concerned about wood movement. Should I cut that tenon into three 2 1/2" wide and 3/4" long tenons and only glue and pin the center tenon or can I just use a 7" tenon and glue the whole thing, which is how the original was made?