I just installed my panels today. As mentioned get the mounting hardware (
https://www.amazon.ca/gp/product/B07...?ie=UTF8&psc=1) then premount them to your panels so you get the proper spacing to match your rafters. Probably 32'' and that'll get you 1 hole on every mount directly into a rafter. You'll want to confirm your spacing with a stud finder. A frosty morning will also give you a nice pattern of the rafters, but the stud finder will give exact,use a pensil for your marks as they'll wash off in a little while when you prepare the area for caulking Then place your panels to match your rafters and mark there positions with a permanent sharpie jiffy marker and the 1 screw hole you'll be making on each mount. then move your panels aside and wash the area soap and water and rinse, replace your panels on the marks, and drill a hole,and just slightly screw in a screw, drill another, place a screw just a little bit again and drill your last 2 holes. lift the panel out of the way, put down your dicor within you jiffy marks, carefully place your panel and screw down your panel. Don't strip the threads of the screw as your rafters are likely aluminum. I didn't like the sheet metal screws that came with the mounts and went to the lumberyard and got a courser thread sheet medal screw. I also never worried about 2 screws per mount as the other hole would only be sgrewing into the 3/8'' plywoog and would be the first thing to let go and crack, allowing water to enter. Now you can do your next panel. Note, today I just used Dicor lap sealant as I had a half tube, that worked perfectly and when the temperature gets hotter up her in Saskatchewan I will add another layer of self leveling, but till then these are absolutely guaranteed water proof. and took me 2 hours to mount the panels on the trailer after placing mounts to panels and marking everything where they should be. That type work is always a lot of fun and tomorrow the 6AWG cable gets ran to the controller.