site doesn't load with include path

[eluser]slapyo[/eluser]
I have a lot of sites that use the same /application/models/, /application/helpers/, and /application/libraries/.

I have them all sitting in /opt/www/includes/application/ and I also have /opt/www/includes/system/.

In PHP I have the include path set so that all I have to do is include('system/...') and it will work. But it's not.

In the individual sites root folders they do not have the 3 folders in application and they don't have the system folder. If I add them in, the site works no problem. However, for the sake of having to edit the same file over and over I'd really like to have one central place for them all to be. Should I make symbolic links?

Ideas, suggestions ... anything?