Klint with a jumbo tiger from earlier this year
We were using the same technique and fly, the only difference was the fly line. I was using my old standby clear intermediate line that I've never really liked due to tangling issues (no matter how much I stretch it). After watching him catch a few fish I realized that I was missing the subtle takes due to the coiling of my line. His line was straight as an arrow, and as I later found out has virtually no stretch so he could feel everything that was going on when the fly was in the water. Klint was using the Airflo Sixth Sense intermediate line with a clear polyleader and 3x tippet.
When Airflo says it's low stretch they aren't kidding! This line reminds me of the braided line I used when fishing for cod in New England. The advantage to this type of line is that you can feel every tap, tug, and wiggle.
The type 7 full-sink line comes with depth markers at 10, 20, and 30 feet that come in handy when fishing vertical with chironomids or balance flies. With a sink rate of 7 inches per second it'll get down to the fish in a hurry! During my most recent stillwater outing I found fish holding in water 7-10 feet deep and itching to chase a streamer. It was fun to feel them attack the fly on the strip!
Don't deny your local lakes, because you never know what might be lurking on the bottom!