ok, HELP. my rear seat mount is loose and one of the nuts is missing. the base is about 5 inch across and has small screws in it. can anyone tell me what size the nuts are. not much room to work with under the mounting plate. just a small hole up to the bottom of the screw. I have pulled carpet back on the deck and found the screw heads. assume I will need to get a socket on the bottom and hold while I tighten the screw from the top.