When I brown a patent or hooked breech, I have a 1/4" length of rod threaded to fit the nipple hole, with a screw driver slot cut across the top. It is not necessary to bottom it or screw it in hard...just fill the hole. I use 6 x 48 scope mounting screws when I screw down an under-rib, and I don't worry about plugging them, but then, like Dan, I like a fine grained matt finish from my brown, so the holes don't get eroded by the process. Unlike Dan, though, I brown the rib with it's rod pipes separately.