This conversation for me highlights how there is still so much for us to learn about instrument design and its relationship to the player. In fact the other thing that became very apparent to me during this process was the difference a mouthpiece can make to intonation (or perhaps more accurately, how large of a difference it can make). I made brief mention about it when I wrote about the testing of the Shires and Eastman. But in relation to the Prestige, when I wrote my previous post I was using my Alliance 3A on the Prestige. I've since swapped to the Alliance 2 that came with the instrument and interestingly it had a significant and positive effect for me personally with intonation on the Prestige, so much so that a number of notes don't require trigger now. And I found that the mouthpiece switch didn't negatively impact any other aspects of my playing, so I'm calling that a win.
I think this experience for me plus what others have said above about mods to their Adams horns really highlights how we all have a combination out there that will fit us, unfortunately it just may be a bit of a process (often with quite a bit of money involved) to narrow that down.
I will say the discussion does make me a tad envious that I wasn't able to try an Adams but this Prestige is beautiful and I have no regrets.
SE Shires Trombone (1G Bell, TB47 Slide, Tru-bore valve), Bach 5GS Mouthpiece
Besson Prestige 2052-8G, Alliance DC3 Mouthpiece
Yamaha YCR2330 Cornet