According to the little knowledge I have 1 1/8 ounces in a 16 bore is the shot weight for the old Eley Alphamax 16 bore with 2 3/4 case. Unless you are loading a low velocity load I;d say that is a bit near to maximum working pressure?
I do not load 16 gauge but I have the Lyman Reloading Manual 5th Edition, some load data in there. First problem for 1 1/8 oz its all plastic wads, next its all American powders also its for 2 3/4 cases. If you are interested pm me and I will try to help.