I can't say I feel the 5 gal are overkill as even the smallest of autos I've done lately fill the entirety with roots, but I've seen people pulling far better results than mine with 3gal so I have to agree 5 gal isn't necessary. When I saw Tang growing with them a few years back I tried to duplicate his grow as closely as possible and haven't really experimented since. I wonder what effect moving the bottom of the pot up higher would have?
I will say that with the plants I have going over the past 6 weeks even the 5 gal might get some runoff soon. My 6 week plants are already taking 3L daily and my 4 week olds 2L. Not sure if it's all about watering the core first, or just better observation of the plants needs, but they're huge.
Beautiful snow capped mountain range pics as well. How the hell do you get them all in the tent?