Here is my favourite suggestion.
Nice way to deal with it is the same way we did the PDRacers. I couldnt find he pics on the building thread.
You varnish the cockpit floor normally.
Then mask off the area you want to be non skid. Measure and plan it carefully so it looks nice. Doing the whole bottom looks terrible. A glossy margin around the edges and up the middle of the non skid area looks best
Better to have a 50mm margin round the front and edges and keep it about a foot clear at the back. Also leave a 70mm wide area up the middle.
Probably need two small patches either side of the centrecase.
Mask off. Corners need to be rounded off – so put some tape across the corners, use a tin and a stanley knife (carpet knife) to cut the internal corners round.
Sand ready to varnish … pay attention close to the tape as it is easy to leave shiny spots by accident. Clean up dust.
Sprinkle some coarse grain sugar or salt or epsom salts over the wet varnish. Using a sifter gives an even distribution. Just so there is an even distribution of grains. Just so it starts looking like the grade of nonskid that you would like.
Don’t push them into the varnish manually, just let them sit. When done remove the masking tape carefully.
Next day put the boat on its side and rinse away the grains. Clear non-skid.
(I didn’t do a good job of rinsing with the first boat I did this to many years ago … and ended up with an ant invasion .. so be warned!)