I'm in your area... Puyallup, actually.

I know what you mean about having a hard time maintaining steady temps in your tubs. I'm using an RBI rack, and it's definitely difficult in our area unless you have a room dedicated to it.

are you using a rack, or just tubs? I would suggest building a rack if you haven't already, and I'd be willing to lend a hand in doing so.

Now, as far as your temps go... Is there a reason why you're using two different thermostats? Since it's a proportional, you can use one to maintain both sides by using a dimmer/rheostat to dial down the cool side. I'll probably be doing this if I feel the need to add cool side flex to my rack. I can help you with that, also, if you need.

And finally, humidity... I can see in my head how it would be entirely possible to have "wet" spots within a tub, since the air is more-or-less stagnant, or at least flowing very slowly. It's the same with temp within the tubs.. The only way to make it the same throughout is to homogenize the air somehow, which basically means add a fan to make it circulate and mix evenly. That's how stable, constant temps and humidity are maintained in an incubator.. Not really an option for actual housing, though, since flowing air is going to bring in fresh, cool air and completely screw up your temps.