You have to be careful with the Artisan Deco because of two things.
1) The finished barrel is not of uniform diameter, but tapers down towards the nib.
2) There is an enlarged ring on both the nib end and the finial end. . I question the esthetics of making the barrel diameter as large as the enlarged rings ... would look odd.
In fact, at the nib end, the enlarged ring has a lower shoulder portion on the blank side. . This lower portion is only 0.481" diam. . So if you turn to that size at the nib end, the amount of meat is only (0.481 - 0.399)/2 = 0.042". . That's the same as on the Sierra, which is too thin.
It would definitely look odd if you turned to the enlarged ring size, but if you did, the meat would be (0.515 - 0.399)/2 = 0.058" only about 0.002" greater than the Zen.
At the finial end, if you turn to the size of the enlarged ring, the amount of meat would be (0.567 - 0.399)/2 = 0.084". I don't think that would look right.
If you turned to the knurled portion size at the finial end the meat would be (0.513 - 0.399)/2 = 0.057" which is just 0.001" greater than the Zen.
(The 0.399" is the brass tube diameter in all these calcs).
So I don't see the point of the Artisan Deco in this context. . It also has a barrel length of 2.984", considerably shorter than the Zen's 3.350".
I am now going to quit this thread. . I am getting a headache from all the arithmetic, and, besides, I don't think that John, the OP, is interested any longer.