Jack A. Zucker: I'd really love to try this. i cancelled my canon 24-70L lens after reading too many reports of softness. However, tamron really screwed me on a 18-270 which had stuck focus. I contacted their customer support twice and both times received an auto-responder with a promise of a followup which never happened. Not sure I'd trust them for support on a $1300 lens. Buyer beware...
Jack, by "auto-responder" I assume you mean e-mail.
Based on my experience with Tamron U.S. service I'd recommend calling directly. In my case, the lens I sent to them had extreme CA. In the cover letter I referenced the name of the person with whom I spoke and I included sample files. They agreed and sent me a new lens within a week.
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