So you installed the PWCDoctor valves and they work pretty good. I thought mine did as well on the ultra. While installing them in the STX-R I noticed something since I could see the inside of the hull easy with the exhaust out of it. Take a look at the pics.
Notice how far these protrude into the hull and will not actually let all the water flow out. I used a hacksaw and cut down the plastice mount.

Here is the finished product. I still need to seal it with some silicone.

Hope this helps. Easy to do only takes a little time and will help keep your hull even dryer inside.