My recommendation is to apply the non-skid that you see on newer F18's/A-Cat's. There are several brands, Seadek and Raptor Decking come to mind. The other option is a strip of non-skid tape:

The final option is basically a strip of the 3-6mm non skid EVA decking along the side of the hull (where your feet go), the 505 guys use a sort of tire-like rubber for this that works quite well.

I applied a full EVA deck to my Infusion Mk. 1 and it was the best upgrade we made to the boat, much more comfortable in all positions and super grippy. I used the 3mm raptor decking.

Scorpion F18