I assume that you are trying to protect the wood. Have you run it without the shingle? Could you paint the shingle white?
Yes, Greg, that was put there to protect the wood, because our last instrument shelter (of the same type) rotted out after several years. No, haven't tried it without the shingle, but painting it white is a good idea.
It might be absorbing some solar energy and heating the enclosure.
That's an interesting point.