My Eliminator 21' has one- ride plate, shoe, (back-cut, I think), loader, diverter. Done by G.S. Marine back in the day (~'95).
I've played with the ride plate angle some, and it ended up where it started.
I've never ran it without one, so I don't know if it helps, but can't hurt.
I'm not running crazy horsepower, either, maybe 470 hp or so. 'AA' @ 4900-4950(good air)
Moving the ice chest beside the motor cover made more of a difference.
A ride plate makes reverse "not forward"(virtually useless) vs. one without a plate.
A nice underwater step for boarding in deep water though.
Dan'l