Strapping outside is always a problem. The white nylon straps with 2 nails won't hold up to the sun, regular steel will be bleeding rust in a month around here, galvanized will buy you a few years but it will still be showing pinhole rust after a while. PVC is corrosion resistant but the UV protection of the straps seems to be weak to non-existent. I actually had a Carlon rep tell me the listing standard did not require U/V protection on straps and covers so they didn't do it. That may have changed since then (6 - 8 years ago).
I always had a lot of tolerance for improvisation in the strapping methods if they seemed secure and more weather tolerant than the products we have in the marketplace.
