It's really all about knowing your gun and how it shoots. A good even pattern is much more important than any particular number in a given size circle. Whenever you can put a good swarm of pellets in the vital areas of a turkey at a range you know and can stay within, you're in business.
A few years ago the 10" circle at 40 yards was adopted by a number of shooters and it has become a standard, mostly for comparison of one pattern to another. I like to see a good "core" 10" pattern and then a good "fringe" 20" pattern. I'm not so much interested in numbers as density.
It sounds like you're ready to go.
"If he's out of range, it just means that he has another day and so do you."