Possible way to install a stern pulpit: Blind Rivet Nut or Nutsert are available in steel, aluminum and stainless steel. And they are available closed off at the bottom of the hole, or open. I have never used them in a watercraft, but I have used them to install hard rubber fender flares on a Jeep fiberglass body. The ones used were from a professional kit sold to shops through a wholesale outfit. So, I do not have a current source. They are sort of like a pop rivet. Drill the hole in the fiberglass, coat the hole with sealer, slip in the nutsert, put the special tool into the insert and squeeze until it seats. The ones we used were for fiberglass from 1/4 to 1/2 inch thick, which may be the reason they would not work. I cannot say how thick the material is where the rail would mount. Also to note, the ones we used for fiberglass had a ridge on each side of the shank to keep it from twisting. Had to tap them in with a plastic mallet. My use with them was several years ago when they were not yet a mainstream item. I Googled Nutsert and came up with lots of places to research. I'll leave that part to the persons with the need... I think I'd start at a local 4X4 specialists. The people who sell the fender flares. Bill Photo Site