I noticed that my A was quite sharp on my TH&C tenor all of a sudden. I looked over all the mechanism, and decided that probably the G key was opening too far. Since it is a simple mechanism, it seems that adding some thin cork under the top arm that rests on the body octave vent makes the most sense. Is this the proper fix to lower the G key height? Or should I be looking for another solution? Obviously I'm not a repair person, but I am mechanically inclined, and am comfortable with making minor adjustments. Any input would be appreciated. Thanks!