Thanks you guys - i actually could have done a much better job - this was just one of my first times actually building something. I learned a lot from it. There's a lot of feature creep going on, part of which is that light that Cheryl noticed. I do intend to do some tests on it and see how it holds up inside tubs and all that. I have 9 feet of wired flexwatt in 3 foot lengths laying around if it needs help with temp maintenance. I'm feeling pretty optimistic (it is reflectix-lined on the interior and underneath the external panels, with a 2" gap of air between the two layers - i expect it to be very efficient especially if i can get some hinges to help me close the gaps in the door).