My suggestion would be to make a custom mount for a holder like the one you pictures to attach to.
Perhaps two vertical bars that are bent 90 degrees at the top and the last inch or so 90 degrees again so its pointed back down. The other end of the bar you can put a pad on where it will contact the side-wall of the camper.
You could put the hooked part of the bars above the skirting of the tent at the top of the sidewall and make a couple of slots just like the ones for the bunk supports on either end to let the hooked end slip in to.
This avoids introducing new holes in to the camper body and you may even find a way to use that rig inside when your done watching outside. My preference would be to find a way to hook to the frame without making any holes. I have attached a wifi signal booster that is 12 feet tall to one of my lifter posts with neodymium magnets and a velcro strap and its been fine in wind for the last few years.
Something like my awesome microsoft Paint image is what I was describing at the top: