David, from my understanding, no.
You can use ali angle or brackets to affix and support, say, bulkheads or mounts etc. You just can't go overboard with the amount of metal structural bits you use, especially in such a way that it forms more of a chassis than the wood does.

Harry, cheer up :wink:
I don't think anyone's going to be completely anal about rules and what-not, just as long as those involved apply a bit of common sense. As PJ said, the idea behind this is more to do with fun, entertaining but visibly destructive battles. But there can't be too much leniency regarding what's permitted otherwise people will bend the rules to gain a possible unfair advantage, something that's not really desired in a fun class.