Here is something that would be a clean way to attach things to the deck. Forget "SUP" and replace with "kayak." You would need a backer block beneath these but other than that it is a simple install and makes a great firm camera mount that is flush when not in use. (I have not tried it- going by the literature.)

http://shop.fiberglasssupply.com/cart.cgi?group=82&child=5835