Fixed the problem of the flange material covering up part of the nutplate’s hole by using a dremel tool and a pointed grinding bit to remove the interfering flange material. Ran screws in all of the holes to insure that enough of the flange was removed to allow the screws to go in all of the way. After examining the firewall shape I believe I will replace the f-421 skin with new one so that all of the screws will line up exactly with less stress on them and so that the skin can be trimmed to match the cowling perfectly.
