1. Install project spezific customizations to [INSTANCE]/src/conf
   i.e. [INSTANCE]/src/conf/MY_PROJECT

2. Rename ESI Folder i.e. to ESI.OFF

3. Create a symolic link to your folder
   ln -s ../../../../conf/MY_PROJECT ESI

(Sorry, that's not zope like, you probably can also do it with overide.zcml )

