Originally Posted by deniseO30
There may be a backing plate already under the old one. Only way to know is to remove it. If there isn't one.. get a alum. bar thick enough for threads (stainless or bronze good too) matched to the new cleat. Loop a string through the holes after dropping it from the holes in the hull.. pull the ends up.. start a screw on one.. cotton string should let the screw start in the threads.. then do the other. It's called "working blind" You could use a single piece of string or line with a 3rd hole in the center sealed after.
Another way would be with really long screws that you can put the threaded backing plate and pull them up through the hull and new cleat, replace one with the proper length.. then the other.. working blind again
that may be worth a try. it would take allthread to reach far enough to grab the backing plate from the access port that is there. there is no backing plate, now. the screw in the rail base turns freely. and you can't screw the cleat screws out because the nuts turn with the screw when you try. but your method would be worth trying before i go cutting a hole in it.
although, thinking about it i don't think it will work for the rail base. which would leave me in the same position. maybe a method for the railbase can be devised using your idea, though. i will have to give it a lot of thought. no holes cut is a good thing. thanks. that's very helpful!