I've got 5 on the top. I've gone through pretty deep water, no problem. I was able to maintain speed, and didn't have a drop of water in the box. I can't say for sure water was flowing over the top of the box, but there was dried up spots on top. The water got to about the bottom of the seat momentarily, on more than one occasion.
I don't have any in the door. Thinking about taking the door off, which would negate having the filters on top. I always wonder if any air passes through them at all, versus taking the easy route through the normal path.
I ride an X, so not too much deep water crossings in my future. Nothing duct tape can't cover up.