I did not understand why the instructions suggested to drill these from the upper side. I was able to install all the doublers with the covers installed from inside the wing and then drill the holes for the doubler plate. All of my wing skins already had pilot holes drilled around the inspection hole opening so I'm guessing that when the instructions were written the pilot holes were not pre-punched in the skins? Either way...all holes drilled in LH wing. I left them in place until I complete the same step on the RH wing so I can remove them all and prime at the same time.