[TowerTalk] copper roofs?

[alsopb]

A friend of mine moved into a new qth.  

Unfortunately (or maybe fortunately) the property has a large
garage/barn type building with a copper roof.  

Crude modeling of it indicated it messed up the pattern of his 40 M
planned beam-- even when it is about as far away as it can be.

Two questions:

How does one model such this large copper roof in antenna modeling
programs?  

Anybody out there do something like put a vertical on top of such a
building ?  My first guess is that it essentially would eliminate
ground losses but beyond that the vertical won't appear to be "over
sea water" because the size of the roof isn't miles across.

Suggestions and insights requested.

73 de Brian/K3KO

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