I understand, LW. I found patterning that my single shot's point of impact to point of aim was several inches low requiring me to float the bead. I didn't like that idea. As you see in the pictures, William at SumToy installed a set of adjustable Williams Firesights on the barrel. Your pattern will certainly kill any turkey out to 40 yards clean.
If your POI is close to your POA, I wouldn't worry about those closer shots if you went with the .670.
Cool little guns. I saw this one on gunbroker few years back and hit the buy now button immediately.