Thank you very much for pointing me at the right bits of existing standards.
Matthew Wronka's reference of a "canonical relationship" and RFC6596 is very much on target. rel=canonical should do as much as I could hope for in any case. I of course considered an initial landing page, but UX pushes strongly where the 99.999% case is not the one which should require the extra click. I'll certainly have the canonical link specified, and hope for the best. Perhaps even, as you say, submit a ticket to a browser or two. Thanks again, Andy Valencia
