zinc roof

I am about to start building the subdeck for a standing seam room, I'm getting splinters while I still procrastinate zinc, steel etc. I have been discussing the supply of Standing Seam from Pagurek with Patrick who has been very helpful but I'm after some pictures or advice from those who have...

I am planning on having a zinc roof and facia and would like a cedar soffit. I understand that rain water run off from cedar can have an adverse reaction on zinc. Can anyone tell me it a cedar soffit will be ok as I assume the run off will not be significant as it will be below the zinc roof...