increase thumbnail size

I need to be able to increase the display size of thumbnails. On an iMac retina 26" screen FM shows 24 thumbnails in the storyboard, but they are all rather small. “Expand visual tracks” vertically increases the storyboard space, but not the size of the thumbnails. Even on standard view there is wasted vertical space in the storyboard. My NEED is to better sequence the images and, in order to do that larger thumbnails would be very helpful.