I finally got around to hanging Christmas lights this year. I bought gutter clips so I wouldn't have to permanently install anything, but I just realized that I don't have gutters along a pitched portion of my roof. The soffit there isn't perforated, so I can't hang them through it either. I did notice the metal flashing (maybe it's flashing? someone correct me if I didn't use the right term) is hung with nails underneath the eaves. Can I nail into that without worrying about moisture problems?