[AT] Screwing roofing

[carl gogol]

As I prepare for a noisy weekend's activity of screwing down the metal roof
on the new shed, I started to ask other people at work how they did it.  I
was very surprised by the response of one friend who said he screwed it all
through the tops of the ridges to the wood so it wouldn't leak.  The
instructions I have found recommend screwing in every other flat (about 16"
on 3' coverage material) and every other purlin or about 4' along the run.
In addition, use a short stitch screw every 4' on the overlap ridge that
just binds the metal and does not bite the wood.
What do you all do?