Disregard, I was able to use the old site MAC address on the new system. You can go ahead and delete site 5372.
For future reference, this is what I was trying to do which sounded like something that would be supported: http://discussions.flightaware.com/ads-b-flight-tracking-f21/new-raspberry-pi-new-feeder-how-do-i-keep-old-stats-t19428.html and I am a bit disappointed that it is not supported yet, as I hate having to make workarounds since eventually they get forgotten.