Looks pretty good Trev. A coat of stain and and some varathane and they should last years.
It's not that much different from my design, but I use 1X3 pine instead of 2X4's so its lighter. I
put my trays in length wise side by side, females on the right and males on the left, so each palete contains a pair of snakes.
These are the Zellers "Truly" brand under bed trays. They are bigger and cheaper than Rubbermaids and more shallow, so you can stack more in a rack(snakes aren't tall). I get 9 layers
in a 5 foot rack, for 18 charges per unit.. I keep everything from rosies to Hondurans in these.
In cases were I need to hold the moisture in, I simply slide a platic desk blotter sheet over the screen. I do the same when I use a tray for and egg laying sight.. Just swap trays with a moss filled one and top it off with plastic. works like a charm