Jim, I do use a full sink (type 6)line to fish water that is deeper than 20ft. Once I have established the depth of the water I am anchored in, I simply cast out enough line (factoring in the length of my leader) to ensure that my fly is within the bottom 12-18" when the line is hanging vertically below me from the end of my rod tip. At this point, I will "crawl" my chironomid vertically upwards through the water column, allowing for pauses at times where I will let my fly hang motionless. The "hang down" or vertical method of fishing chironomids off a full sink line is a great way to cover the deeper water that chironomids live in (they can live in water 30+ft deep). I prefer this method to the long leader/floating line/indicator method (which I will not use in water deeper than 20ft)