Dear Ethan,
Jason is out for about a week, so I thought I’d point you to some documentation you can look at for now. He has often talked about the FAST theory basis here and searching this forum for “fast theory” may help you find a few more articles that will help you. However, his post of Dec. 15, 2010 in the Coupled blade modes in FAST thread seems to collect much of the information. Please review that posting.
Marshall