ALuminum jig plate - cheap surplus
 

In the event that anyone needs cast aluminum tool and jig plate made from MIC-6 alloy or the equivalent, this place has good pricing on leftovers from their machining process. While not as strong as some alloys, it is precision ground and very stable. Too bad they don't have anything thinner than 5/16". Who knows, maybe you could talk them into giving you a plate or two :D

http://www.sandsmachine.com/alumweb.htm

If you need to make a turntable base, it might be useful. Might also make decent side plates for a transmission or something.