Originally Posted by
rpenmanparker
I'm not sure I understand. Is your saddle all the way back on the current seat post and you still need more. Or are you trying to avoid clamping your saddle more forward of the middle of the rails. If the former, you need more setback. If the latter, just push the saddle back. Contrary to popular belief there is no reason the clamp needs to be centered of the saddle rails...or even close to that. If you need more setback, there are seat posts with 135 mm. Here you go for a suggestion: Specialized Alias seat post with 35 mm setback. Without getting some monstrosity, that is about as long as you can get.
RPP, the adjustment zone of Brooks rails is not much more than the length of the clamping zone of a typical seatpost. Generally you don't have more than maybe 10 mm of wiggle room. By comparison with a Selle Anatomica you'll have at least 30 mm of clamping zone. If you also go with a long-setback post like the S-84 or (haven't seen one yet) Velo-Orange, you have enough potential setback to look truly strange if you do full-slam.
I haven't seen a Specialized Alias seatpost. But a Specialized Alias saddle shares with its siblings (Toupe, et cetera) a very long adjustment zone. But its a little less than the Selle Anatomica. Now I don't know how much the adjustment zones overlap. I could imagine a Spec providing a better rider fit with some seat posts than a Sella A.
What does he need? Well yes, that is the question, for each of us.