I was checking the contents of my Aperture 3 library, and noted that the size of the folder containing my thumbnails is almost 11GB. In comparison, my previews only occupy 6-7GB. I have around 17,000 photos. The previews are 1920x1920, in quality set to 8. How can I reduce the size of the thumbnails? Or is it possible to disable previews and just use the thumbnails files in iLife and when not having the referenced photos connected being able to rate and see my photos just like if I had previews? Thanks.