Have I reinvented the wheel? I found the standard rubber sanding block too stiff for wet sanding highly curved surfaces such as a kayak deck. My solution was to place a sponge between the sanding block and sandpaper. This has the added advantage of carrying water which squeezes out of the sponge as you sand helping wash away the varnish particles as you sand. I am using a standard rubber wet sanding block 2-5/8 X 4-3/4 and a 2.7 X 4.5 Heavy Duty Scrub Sponge with Scotch-Brite on one side.