I don't know about other brands of roofing (I used Laserlite), but one tip I have got is make sure you use the screws with the attached "saw" blade (for cutting the 10mm hole as the screw goes in).
I think they are called one-step screws (or something like that). They make the hole (pun intended) job a lot easier and quicker.
Sorry for not answering your question ... but I hope this info helps.
Bite off more than you can chew and then chew like crazy.