I lowered the weight of my shot load from 1 1/8th oz. of #8s to 1 oz. No change in score.
I lowered it to 7/8ths and then to 3/4 oz. no change in score.
At 16 yards you want the most open pattern you can get that does have holes lager than the target at the range of impact. I like #8 shot at 16 yds because it puts a little more lead out. However, I am VERY quick on the trigger at 16 and most hits are "smoke" even with an open choke. If you are slower on the trigger the smaller shot may cost you targets at longer range unless you tighten the choke.
You don't actually mean 16 yards, do you? The edge of the Trap house is at 16 yards.