Galv. is fine... it will never get hot enough to be a problem... unless it catches on fire..
After a few years of testing my mailbox mod on a regular basis, I can say with all assurance it will NOT catch fire.
How can i be so sure?? My "mailbox" is home made from leftover 3/4" PLYWOOD!!
Its well smoked by now but doesn't show the slightest heat discoloration.
Gary