If you are looking at shooting them on the wing you might be better off with larger shot than #4. #4 shot thickens up the pattern over larger shot but the larger shot has the advantage of better penetration down range. So three hits from #2 may impart more energy than five or six hits from #4's.
#4's and #5's are fine for head and neck shots where you need multiple hits to be sure to hit the spinal cord or brain area but how deep will they penetrate on a passing shot to reach a vital area? Two or three inches to get into the body cavity in many areas is the minimum. The bony rib, back and breast area are a tough nut to crack. Just like a up the rear-tail shot, also know as the Texas barin shot, on a goose is a real bear to bring down a goose whitout real large shot at a decent range. Killing a turkey on the wing, at any great distance, can be hard to do.
I would try 1 1/2 ounces of #2 or larger shot, with buffer, if possible. If you get good center pattern density at 25, 30 or 35 yards I would be very happy. Better to have a tight center pattern than an evenly spread pattern. Five or ten yards is a lot easier to deal with when you start out with tight patterns.
