The other alternative is pieces of ply mounted just outside the hatch that can swivel over the hatch. I've done a couple boats that way and prefer it as it provides nothing to be grabbed. The webbing and cam levers pygmy uses work but be careful how the lever strap can get dislodged. Webbing and buckles are ubiquitous but all it takes is grabbing the webbing in a rescue/panic and that fastek buckle will break. I've used them most of the time but it's not really what fastek buckles were designed for.