Im installing a tin roof, but have only ever installed polycarbonate before, so I have a couple questions--do I need to pre drill the hole so the metal has room to expand and contract? Also, do I need the wavy spacers like I do with a poly roof panel? And lastly, is it possible to overlap the roofing panels too much? I'm trying to get out of cutting it. It's a simple slanted flat roof so there are no joints or anything. Also, anything else crucial I might not know I'd really appreciate! Thanks!