Hi James, Most of us have this problem except for the pro's and there are a lot of them on this site and some of us are a bit more clever and make the marriage much easier.I have come up with a cockamamie idea that works for me: I use a 2" wide x 6or 7" long piece of aluminum
about 1/16" thick (roof facia or screen door panel) and bend an L about 1/2" on the end then sneak it under the deck and with a gloved hand pull the strip and push the deck and tape it off
also use a nylon strap to hold things.Don't use steel,I ben't a thin blade putty knife,it worked wonderful until I tried to remove it OH what a mess. Next boat's shear will be hard wood with cove and bead shear only.(hope no one is laughing too hard) Good luck with your build Nick R.