Agreed. Wonderful job building it. It looks very well constructed and effective.
I will have to agree with Becky in that ventilation is your best friend when breeding rodents. In fact their health and well being depends greatly on it. I hope I can offer in my limited experience with rat and mouse (I suck at breeding mice) breeding some suggestions that will allow you to keep your design and with very little editing your great work and time and money spent allow you to rock the rat world.
Understand these are only suggestions of ideas I have to help ventilation
First: you could simply remove the plywood on the sides and have a fan blow on it to allow air flow across the tops of the tubs. Problem solved.
Second (in addation to the first or stand alone): cutting out the sides of the tubs and pop riveting hardware cloth in its place to allow air flow.
Third: you could remove the board the tubs sit on and suspend them like this http://www.ralphdavisreptiles.com/in...ves/oct-03.asp
to increese the amount of air space between the tub and the one below it.
Just my two cents great work building it. But with some minor minor tweaks will have you over run with rats in no time