On lighting requirements for autos, I have found more is better up until about 20/4, then it a tossup. And by more is better, I mean as much as you can give them for as long as you can give it to them.
Just like with photos, higher light intensity will get you stronger, more resinous buds. With autos however, the more hours you can give them, the bigger yield you get.
I have started autos under 24/0, 20/4, and 12/12. I have had reason on occasion, to put the 24/0 or 20/4 in my 12/12 photo box. The only thing I noticed was a smaller yield from the autos that were started or moved into the 12/12.
Potency was the same, no problems with hermie's.