Ive got a 20 and a 5. When the 20 gets low, the 5 goes in until I get a chance to refill. It also gices me a loos tank to flush my kegs with co2 at kegging time
I have had numerous conversations with the electricians at my work about gfci breakers and gfci outlets (and witnessed issues mself). And I was told that if you have two gfcis on one circuit (gfci breaker, outlet, and/or gfci plug) you can have issues with constant tripping. Not saying...
Drain hole is probably the safest bet. I'm in the middle of converting a freezer, and the interior of mine was just lined with foil, so I was able to carefully (and lightly) cut the foil and insulation away until I got to the outer shell, then I drilled through the shell only....
grainger maybe? CED, unless you have a graybar nearby (www.graybar.com) sometimes graybar won't sell retail, you'd have to go in and ask. You might have other options, but you'd have to talk to a local electrician.