I should have been more specific: I'm referring to the type of fastback seatstays used on this Trek, the type I believe was invented (or at least popularized) by Cinelli, where the seatstays are attached at the seatpost binder (and are pinched together by the binder bolt). (I am not referring to "fastback" seatstays attached some other way, e.g., mitered and brazed to the back of the seatlug or seattube.)
Lee Berg
Palo Alto