I hate answering my own question, but I figured it out on my own. I movie 13 will only allow you to reduce the time interval for photos to a minimum 0.2 seconds. I could never figure a way around this. I did find a free app on the Mac App Store called Zeitraffer. This was very easy to use. Put your photo stack in a folder, pick the folder and then hit export. Then name your video, decide how many Frames per Second (Frame Rate) that you want (I like 24) and output size (resolution: 1080p would be 1920 x 1080). hit go and your movie is made in a few minutes. From here import this movie into iMovie so you can add it to the rest of your project.