I re-read your post, #14-#16 sulfurs, big bugs. I have not seen any 16s this year. When the bugs are coming off in numbers and the fish are refusing every size I have tried, I go to a #17 cripple c.d.c. sulfur. They will often take it and when they stop I go back to #20 c.d.c. sulfur with a zelon tail.
I have a scale for measuring the amount of bugs coming off. When the bugs are pouring off in sustained amount of time, I give that a 10. when they are coming off in singles and with little frequency I call that a 1. What I have seen this year on low water is about a 6-7 and that was in July.