Pete Ramey's website hoofrehab dot com is a good place to start reading about trimming based upon the research of Dr. Robert Bowker of the Equine Foot Lab at Michigan State University. Here's an article on Bowker's work relevant to "navicular syndrome":
article on Bowker's work:

http://www.hoofrehab.com/Navicular_story.pdf

Where are you located? I have been trimming using the "physiological trim" recommended by Dr. Bowker for three years now...I am in San Diego.