Success
After apparently stripping interior so panelbeater could get at body shell to "widen" the gap between inner and outer skin where touching when body flexed, looks like noise is finally gone!
Only taken almost 3 years, but I guess perserverence pays off...
And kudos to my dealer service manager for standing up to VWA and insisting that mods, while possibly making it more noticeable due to stiffer suspension, were not the cause of problem