Want to fit a 100w panel to the roof. I've read up on the technical stuff like controllers etc etc but cant seem to find anything on the actual practicalities. Is it screwed to the roof? I mean straight through the skin into whatever is underneath. Running the wire to the controller (do i drill a hole?etc etc. I've seen a couple of vids on you tube but still not confident. My main concern is causing leaks. Any ideas where i can get the advice, instructions?