For the transom bands, I used #6 Sharx SS screws. Mine were 3/4" long and they went into the frame as you can see in the photo below. So there is no screw protruding through the hull. My transom bands are 2" wide and that transom and frame are also thick I used either Boat Life caulk or GE outdoor waterproof caulk to seal the holes. I placed a small dab onto the hole and then a small line of caulk onto the threads of the screws. The screws pull some of the caulk into the hole and the rest formed a seal on the hole in the transom bands. Mine were made by cutwaters.com
No screws are showing.