Hi Chris,
Its really just the shape of the rocker box, the face of which directs the airflow form the rear mounted fan across the face of the mirror. If you look at Tim's article on making the scope, you might get an idea of how it works
http://www.iceinspace.com.au/63-324-0-0-1-0.html . I did use an internal baffle and neoprene sheet as per Scott Tannehill's article
http://www.iceinspace.com.au/63-400-0-0-1-0.html on my erstwhile GSO 12" dob with very good effect. I didn't have to remount the fan as he suggests as the fan didn't seem to cause much vibration anyway.