John,some states forbid any covering of the rear license plate.Texas is one.
If the top and bottom panel lengths are equal to the height of the boat tails rear bulkhead,you might swing the lower panel down and under,away from the plate.
The upper panel might have to slide in like a cutting board in a kitchen cabinet/metal desk sliding shelf
http://images1.cableorganizer.com/mi...MA-SSHD-28.jpg