I have been looking into the feasibility of mounting the GT subframe to my SDR, so I can use the panniers. So far I have not seen any technical problems. I haven't measured anything either, yet, as I don't have access to a GT. In no way shape or form am I really knowledgeable about these kind of things, so I was wondering if there have been more people checking out the feasibility.
My guess is that I would at least account for the extra weight and adjust the rear dampers settings.