PharmerBrown - I have the model 389 as well, and it was one of the best investments I made in my deer business. The worst investment was buying the deer in the first place!!
I use the green charges, and at 10 yards I used 1power...20 yards/2power...30 yards/3 power and at 40 yards I used 4 power. I never shot past 40 yards, but I believe if you had to, 5 power would be used at 50 yards.
It was nice to have a 10 yard range with that gun. That way I didn't have to pack my pistiol around for the shorter shots, and all that went with that, ie pistol in hand when you should have had the rifle...rifle in hand when you should have had the pistiol.
You must be careful judging distance because you can run the dart into the deer, which is another reason I preferred the area right where the neck fastened into the shoulder of the deer. The hide is much thicker in the neck, plus the deer more frequently offers that perpendicular angle in that area of the neck that darting requires. I got to where I didn't even like the hip anymore. It seemed sometimes to take longer for them to go down when hit in the hip.
Shoot and sight your gun at all those distances to make sure your're spot on, and remember that deer are almost always closer than they look.
Hopin the best for ya PharmerBrown!!!