Ok, I was able to get this working. Not sure if this is the best way, but it works for my purposes.
With this change, the behavior is that selecting to view the full site will show the desktop version, and clicking nav links will show the desktop version, but upon exiting the site and typing in the main .com url again, device=auto is added to the url and it will show the device dependent version once more without clearing cache or doing anything else other than reloading the URL.
I just used htaccess like so:
RewriteEngine on
#
# Rewrite to append "device=auto" query string to .html, .htm, .php, or index
# files at any directory level, unless that query string is already present
RewriteCond %{QUERY_STRING} !([^&]+&)*device=auto(&.*)?$
RewriteRule ^(([^/]/)*[^.]+\.(html?|php))?$ /$1?device=auto [QSA,L]
this does not appear to have any negative impact on any other aspect of my site, YMMV use at your own discretion etc. etc. etc.
Hopefully this is of use to someone else.
Thanks,
D
