Someone posted about building a copper wood burning stove on another metallurgy forum, and the consensus was that copper is just way too expensive and it gets too soft at the required temps for secondaries to burn (it becomes plastic). Also from a design perspective, copper is just too good a heat conductor to allow temps to reach the needed temps for secondary combustion to occur and the plastic/deformity issue would not really be an issue. So in the case of designing EPA type wood stoves, copper seems to not be the choice in materials with the added requirement for a firebox material with a lower heat transfer rate to allow temperatures to get high enough to burn wood cleaner. Reverse-intuition strikes again when it comes to EPA stoves. Lower heat transfer metal allows for higher temps in the firebox to burn cleaner and more efficiently. Doh!