Before you completely hate your Susato, have you tried the MT-Guru O-ring Tweak?
It will make the last 3 notes of the second octave better and less shrilly. I have also noticed that in my recording in a software, the O-ring makes a difference in the wave scatter, that is, the sine/cosine waves are much closer.
Try it. Im not sure how to link the thread created by MTGuru here.
I have a varied opinion with Feadoggie. I have both Susato Bb in S-Series and in M-Series.
I liked the S Series over the M- Series.
IMHO
Bb S-Series sounds a little quiet compare to B-flat M-Series. I guess that is why this is discontinued. But I wonder why they made an Oriole in a similar bore size.
Bb S-Series is easier to control compare to the Bb M-Series. If you want a louder whistle you might hate the low octave of the S-Series.
The M-Series B-flat has a hard control over the last 3 notes. In comparison with Key of A, were the last 3 notes are easier and less push.
I have also read a post here I think from Jerry Freeman that he blunt the blade a little just a little with an exacto knife on his Susato G- M bore and it improved the sound. I did that and it did made it al ittle easy to shift on octaves.
I have also read in some post that Susato has an embouchure technique for it not to sound shrilly.
I have to say, based on my experience, (DISCLAIMER: THIS IS BASED ON MY EXPERIENCE AND EXPERIMENTATION, IT IS NOT 100% GUARANTEED)
you need to pout your lips out as if pronouncing the pure vowel “U” or “Tooth” (without the T and th) when blowing it. Make sure also that the opening of the U position is narrow enough to fit the air passage of the beak. It is similar to the flute, but the air should come from to middle not from the top or slanted in some way. This is for you to direct the air flow.
For you to visualize the mouth position, it is like kissing the Susato Large Beak, and not putting the Beak inside your mouth.
Soft palate should be lowered and not high to control the air velocity’s consistency. Doing this makes you control your natural tendency to overblow. With this , it makes you shift your octaves smoothly on a Susato. I have noted this difference on the Low D where when you hit the First octave B and then the Second octave F in single breath. This also applied to the M-Bore series.
I don’t know if it is me, but try raising your tongue in your front lower incisor teeth rather than making it rest in flat position while doing the positions mentioned above. Do not over raise your tongue, raise it to the level just enough to touch the incisors. In this position i seem to hear the Susato sounds sweeter. I have noted the effects specially on the M-bore to the L-Bore, and minimal on the S-Series and quite irrelevant to the VSB series.
Try experimenting on these. Otherwise sell your unwanted Susato to me on a lower price. 