Sounds like you’re going through the same thought/stress process I went through to mount my TV in the bedroom – boy what am I going to do if I mess this up. I too had the round sticker mounted on the wall telling me to mount TV here (on my trailer outside wall). What would have been nice is a few more words of instruction on that sticker i.e. what am I screwing into (wood, plastic, fiberglass), maximum length of wood screw, should I use a wall anchor, etc. I went to my doorframe going outside and measured that wall then subtracted ¾ of an inch to give me some extra insurance that I would not go straight through.
Good luck with your install. Happy camping.
"We were not placed on this earth to see through one another, but rather to see one another through!"
2013 Timber Ridge, 2013 GMC Sierra 6.2 L