This doesn't answer your question, but incase you are interested and didn't know, I thought I would share.
You don't HAVE to have iPhoto copy your photos into a library if you don't want to. You can just have iPhoto point to their location. You have to make a new library to do this though (as far as I know.)
To do that, hold down the option key when you start iPhoto, then name your library. Click on iPhoto in the menu bar, then preferences. Click on Advanced and uncheck "Copy items to the iPhoto Library".
Of course, you CAN change this in your current library, but I believe that only effects future imports. It doesn't change the photos you've already imported (copied) to your library.