That #11 cap works just fine. If you really want to thump one..
100 grains of Pyrodex RS, then load a 3-1/4 hard plastic shot cup, and equal shot cup of #5 & #6 shot mix, then a plastic foam over the shot card. I hunt with this. It will take one at 40 yards for you. I have a red dot on mine, and I just put the circle with the dot on his head and pull the trigger. This shotgun does have some recoil to it...
There are others that shoot the same gun and I am sure they will share their load. I want to pull the red dot and grouse hunt this year with it. But instead of the 3-1/4 cup go down to a 2-3/4 cup.