There is an inherent intonation problem with (at least some of ) the #1 alto TT necks. Tones above high A get increasingly sharper. This intonation issue is the same with every mouthpiece I've tried, including the original Buescher TT and the Caravan large chamber. The problem is in the taper of the first 5-8 cm of the neck. This was corrected when Buescher produced the #01 neck for the Aristocrat. The bore of the main body of the TT alto and the Aristocrat are identical down to the slightly bigger bow and bell of the TT, and if you put a #01 neck on a TT alto it plays in tune. So this is not a mouthpiece problem. If you put an insert of the correct volume at the right spot in the neck, the intonation gets correct. This also shows that it is the volume of the different parts of the bore that decides the intonation, not the shape of the bore. A small piece of a rubber hose placed at the correct spot makes the trick
My method is a do it on the kitchen bench at no cost type – and you don’t alter the instrument permanently.
You take a hose made o PVC or silicon rubber that has a diameter slightly bigger than the inner diameter of the neck and a wall thickness of 1-2 millimetres. You cut off a piece of 1,5 cm, stand the piece on the table and cut it into two half cylinders, one piece a little bigger than the other. Then you take the biggest one and place it against the inner roof of the neck. If you have silicon rubber it will stick by itself – PVC will need some contact glue. The placement should be centred aprox where the cork ends.
To fine adjust the size and placement of the piece you first have to have a correct placement of the mouthpiece. I do it this way : adjust against a tuner with both F sharps and then keep the embouchure fixed playing from high G and up. If the piece is placed too far into the neck or it’s too big the high A will go flat. If the high B and up still is sharp the piece is too small. Check also the ordinary high A fingering against “ the control high A” -- finger A + G sharp without the octave key pressed (total 3 fingers).
To make a permanent fix you have to retaper the neck internally to mimic the Aristocrat’s "01" neck to about the point where the octave vent is. I've done this using a metal epoxy putty.
Please ask if you need more explanation
ToreH