Be sure the install the braces perfectly square with their ends perfectly aligned with the edges of the panel (remember, both the braces and the panels are exactly 11-1/4", so this shouldn't be hard to do). To get it exactly right, clamp each brace in its position, drill two 5/64" holes about 1" into each brace, and drop a #4b finishing nail into each hole. Then you remove the nails and the braces, apply carpenters glue, replace the brace, push in the nail to assure the brace is properly positioned, and clamp. The purpose of the nails is to hold the braces in exactly the right position on the slippery wet glue. After the glue has dried you should pull the nails.