Feelsgood, while polycarbonate may be bulletproof with enough thickness (which may be comforting in pirate infested areas) this is of little value when being overwhelmed by a following sea, stiffness is what is needed along with a large bearing surface at the edges and only a shallow taper which means you need to lift
them further to remove them but also means that they wont jump out if you dont have them locked in. I have seen many coastal cruisers with washboards that i can push in the middle with enough force to flex them enough to pop in, one big wave from behind would likely sink those boats even if their washboards are thick enough to be bulletproof. The good old thick teak
or cored composite boards are stiff and hopefully wont. A 18mm plastic washboard or even marine plywood
washboard is not as stiff as a teak
board of the same thickness and a lot heavier so a poor choice imho.