Even though you seem mostly set, if you're curious, here are some links to my plywood tank build and humidifier.

My sealing probably wasn't as good as you should do it - I did try to coat the inside pretty liberally with some nontoxic sealant, the name of which I forget, which is supposed to protect well for humidity (but not actual soaking in water). I haven't had a problem yet, but my walls and floor are also all covered with regards to the humidity output.

The main design point you might want to consider is a false bottom. Mine is aluminum, which is pretty inert and water-safe, as well as super easy to clean. i like being able to put heaters and such under it ( i have a 2" space underneath), and for heating I use a combo UTH (with thermostat) and radiant heat panel.

http://www.ball-pythons.net/forums/s...ad.php?t=60582

Humidifier, and finished tank w/ deconstruction pics
http://www.herpcenter.com/general-co...age-heavy.html

I prefer homemade tanks, personally, they always work exactly as you want them to, at least thats the hope. The gaps in the doors provide plenty of ventilation for me, as well as maintaining humidity.

Good luck!

Jim