I just put in a holding tank in my boat.
For the vent I just put in a white plastic .75 inch diameter through hull. No screen.
I put it on the side of the hull.
Sounds unusual, but here is my thinking..
I wanted the extra diameter (1 inch dia is probably even better) to fight smells in the holding tank.
I routed the hose uphill inside the hull before it went downhill to the holding tank. This is to keep rain from filling up the holding tank.
I put the hole in the holding tank as far inboard as I could, so that if I burried the rail in the water, it still wouldn't fill the tank.
So, you're good. With the hole on the side, it is out of the way, and large.