I hate to be a party-pooper here, but the way Kirk is building the rear stays will add compliance to the rear tri. While everyone agrees that the triangulated form of the rear, um, triangle is inherently stiff with the seatstays loaded in compression, that is not the case here; he has taken the seatstays out of a compression and bent them such that they will be susceptible to bending moments. I don't think Dave is making any outlandish claims about the effectiveness of the design. If I recall correctly, he commented that its movement is in the 2-3mm range (around 1/8") which I find completely believable and in accordance with my own "testing" of radically bent seatstays.
The argument that whether this 1/8" or so of movement is significant in regards to suspension effectiveness given the compressibility of high pressure pneumatic tires or even saddles is always an issue, but I would ask those in the "con" camp to carefully consider the ubiquitous soft-tail MTB design and the effectiveness of 1/2"-3/4" suspension travel considering the volume of a 2.1" or larger MTB tire.
Cheers!
Don Ferris
Anvil Bikeworks, Inc.
Littleton, Colorado
Ph: 303.471.7533 / 303.919.9073
Fax: 413.556.6825
http://www.anvilbikes.com