I have put this experiment into the circular bin. It lacked sufficient insulation to maintain temperature when the house temperatures cooled at night. If I watched it during the day it worked ok for a 4 hour activation of starter. Beyond that, the lack of cooling made it expendable.
Purchased a Koolatron C18, which is similar to Thermokool MR-318 (not the 138). It lacks the clear front door and is slightly smaller inside. So far it has held the temperature very accurately and the lack of window is not a big deal. Will try to provide more details in a new thread as I use it more.