Hi Mboy,
They sell (which I use) a nut that is attached to two pieces of plastic that move up and down. This also pivots the nut.
So, you drill the hole. Send the plastic/nut contraption in through the hole. You then adjust the nut to be parallel to the floor (it is a nice size wing nut so it will hold like a backing plate). You then tighten your bolt. The plastic pieces snap off flush.
Very awesome solution instead of cutting an access hole in the deck.
West Marine sells them. I will get you the name and link later as I have to run now!
Thanks,
Ed