Hi, concerning the “air leaks around the mouthpiece” of your SS:
The mp has two O-rings to ensure a tight fit. Yours have them, I assume?
If so, and it does leak air, try lining the grooves of the O-rings with a bit of cotton thread, or dental floss, to give the O-rings more grip.
You had mentioned having given your Tectonic away. Got it back, to experiment?