this works great. I've been thinking about making one of these for some time and your tutorial really helped speed the process along. I ended up using an old 2 bay sink that I cut in half (so now I can build 2!)
Additions I'll probably make:
(1) a small fan at the top of the chamber that pipes the hottest air at the top of the chamber down to the bottom.
(2) a strip of waterproof LEDs, or multiple strips, so that the first seeds to germinate don't become leggy
(3) if i can't find a chest freezer, I'll probably make a simple frame out of aluminim and side with poly plastic panels. perhaps then I won't need the LEDs. I'll put a in an area of my seed starting area that gets indirect sunlight.
(4) I ended up using a thermostat that I used to use with my heating mats. it has a remote, wired sensor, so that I can place the actual thermostat outside the chamber. I think Durostat makes a model with a remote sensor--probably a bit more expensive, but easier to set and read temp + you're not taking up valuable interior space.
thanks again. since I've never work on/with water heaters, I didn't realize water heater elements were so cheap and available.