6v to DC input jack seems to work fine?

Hm, that's odd, not sure what would be using that much current. I was only running a LED blinking sketch when testing the adapters and checking the vreg heat. The LED was wired in series with a 1k ohm resister, and was only drawing ~5ma. With the 6v adapter the vreg ran cool, but with any of the others which input 11-13v, it got warm to hot.