some info here regarding the hex patches, monster grip, etc.
www.seabreeze.com.au/forums/Stand-Up-Paddle/SUP/Diy-deck-grippad/Have you considered rubberised cork? I purchased 1 of these
http://www.ebay.com.au/sch/i.html?_trksid=p5197.m570.l1313&_nkw=3mm+rubberised+cork&_sacat=0&_from=R40with a view to using as deck grips. A bunch of circles.
I ended up scoring a new deck pad for $30 so didn't follow through on the cork circles. 3mm rubberised cork can be purchased in sheets cheaper than suitable EVA. You would need some decent spray adhesive eg 3M.
Cheers