There are 6 screws sticking out the bottom of my hull about 8" apart. I cant get to them from the inside. My only option is to repair them from the outside. I was thinking I can shear the screws off at the surface, then either bend them up into the sub-floor or grind them with an endmill. Either way ill end up with a 1/2' hole. can i patch the hole without backing on the inside and if so how?