Your good to go with those numbers, but I will tell you that I have had trouble with 2 ounces of shot in a 3 inch gun in the past. If you can get 1 7/8 ounces of shot that might help at longer ranges. Also, you are right about 6's and their limited range. Number 5 shot is a better choice. I wouldn't mess with mixing shot sizes. Each pellet size has different ballistics and you want your pattern to be in a uniform trajectory.