I finished building a set of plantation shutters as seen on The New Yankee Workshop series. One pair of shutters has 14" slats and another 30 1/2" slats. A couple of the longer slats have warped and give the effect of uneven spacing. The shorter ones are fine. I've used Basswood for the 1 3/4" wide slats. Obviously longer material has more of a tendency to warp. Is there a limit to length in shutter application? Should the 30 1/2" width been divided into two panels? Any suggestions to future builds are appreciated.