I know what you feel as I just went through the same issues in trying to get close head and shoulder shots. FWIW, even the 150 Sonnar does not focus close enough for tight shots. I had come to rack it all the way to closest focus, and then rock on my heels back and forth to focus.
I have yet to try it as it just arrived today, but I received the 16mm ring, and it looks just the thing for the 150. On the 80 however, you will be really "in your model's face" as furthest focus places the lens about 50cm away!
To hijack the thread, does anyone have a suggested exposure compensation for the 16mm ring?