I did what you say earlier (I worked out where the file should be linked), and it doesn't work.

The plugin doesn't show up in Opera (running Opera engine) when you click to view the plugins. Sites like YouTube don't detect any Flash plugin. Opera also becomes a little unstable and crashes more.

Somebody may contradict me but, unless you've sourced the Flash 9 plugin file from some source other than an 800, this simply can't work for Opera running the Opera engine.