Having multiple versions of the manual online sounds all to the good to me. As long as it's being done at all, I wouldn't hesitate to put up the manuals for every release, not just the major releases. For 1.16.x, I'm afraid I rather broke the previous rules for major releases anyway.
https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-<VER>/ What I don't like about this approach is that it redirects from the generic url to the versioned url. Also, the /savannah-checkouts/ seems pretty ugly. I think it would be cleaner to create and commit <www>/automake/manual-<ver>/<files> for whatever <ver>s desired. Could probably get them out of CVS. Then automake/manual/<files> could remain unchanged, as a copy of the current <ver>. FWIW ... --best, karl.