interference from metal pickguard?

I want to make a custom copper pickguard for my P-Bass. I'm wondering if it would interfere with the pickups. Copper is not, as far as I'm aware, magnetic, so I imagine not, but maybe someone here knows for sure. I'm thinking it would need some kind of insulator on the inside, like a layer of rubber or some such, for reasons of conducitivity...
little help?