Excellent suggestion on the washer/flange. You could also use a metal vessel for better structural support and wrap it with insulating material - maybe a cheap aluminum pot?
I absolutely use a GFI - see schematic of the system here
It's a standard 1500w water heater element, any hardware store carries them along with a fitted gasket (which as I discovered, doesn't seal against the plastic as well as it should)
Definitely had some leaks to start, and had the same experience with the hi-temp silicone. I ended up putting a rubber washer on the inside and a small o-ring on the outside (and a new layer of silicone), did the trick
After buying a bulk bag of 5/8" washers last year and selling off the extras piecemeal, I just found the same vendor now sells them individually for $0.25 a pop:
http://www.boltdepot.com/product.aspx?cc=12&cs=64&cm=6 (product #2951)
I'm doing something similar, using snow/ice water in a 2.5 gal cooler with a submerged coil and a trusty March809 to circulate water between the IC and the coil in the cooler.
I'm many years removed from my engineering classes - will the evaporation rate in a full boil be higher or lower at cold ambient temps (assuming equal humidity)? I'm celebrating MLK day by brewing a British Bitter - close enough:D
Just guessing, but I think what Dave is suggesting is do the full boil with a 'pretty close' amount of water, and to the extent you're short the target volume due to evaporation, just top off that last little bit with extra water.
I think that's PrintShop's 8-bit history showing through - when I print it comes out looking fantastic. Same with the shadowing; it looks terrible on the screen but the gradient is smooth when it's printed. Can't complain about the results, but the GUI leaves a lot to be desired.