Dr of BBQ
What is the line coming out of the top of your water tank? Is that your supply line? And what is the small line on the water tank top?
Venting your freshwater tank is very important to relieve the tank of air as you fill it up with water.
Additionally, I think its essential to think about a larger overflow measure. Say you are filling your tank up via hose, and you got it connected from the outside (presumably). How do you know when the tank is full? If you step inside to monitor it and it gets close to full, even if you are late to shutting off the hose, you won't have pressured water shooting out of your vent. If you have an overflow coming out of one of the top exits, you can route it back outside, or to your greywater system.
Anyway, this is all off the cuff, but rooted in experiences I've had overfilling my tanks.
BTM, did you consider mounting your tanks under your rig? Right when I got mine, I looked underneath and noticed there was space enough for a 35 (fresh) and 40 gallon tank (grey) on each side. I like your interior mount, but I can't help but think that space is ideal for food storage or other things you don't wanna put outside or under the truck.