I ordered one of the TNC tacks for Christmas. It has arrived however since it is one of my presents I cannot open it until Christmas Day. I will give you plenty of data after that.
I bought the TNC because I just got tired of inconsistant readings with my Hanger 9 and having to get it so close to the prop.
I do a lot of evaluation of engines based on their RPM and I am getting uneasy having to hold the H-9 tach so close to the prop.
More information coming later.

Lee