Jon, FYI, I am currently
a (customized) ancient version of OpenACS 5.2.3, on a fairly recent
NaviServer. I needed to hack some things in that old OpenACS code
make it work with the newer NaviServer, but it wasn't that hard. At
least it was much easier than I expect a full upgrade all the way to
OpenACS 5.9.1 to be.