Well, Mr. double A, I recently did a jazz bass with a rear rout, and I must say the rear cover plate was just a little disappointing to me as it was made from black pickguard material. I ended up using it because it was a nice, easy substance to cut, and I mounted a battery box to it.
Raphohl, I might also suggest that you contact DangerousR6 if you're interested in a metal cover. See info here: http://www.unofficialwarmoth.com/index.php?topic=2754.3000 An example would be post #3004 in that thread.