Originally Posted by Road Fan

Ok. Are you measuring perpendicular to the axis of the seat post, or horizontal (parallel with the ground)? It will make a difference.

If you don't need the short nose of the B17s, I agree with Fiets, that the Selle Anatomica would help you get adequate setback without a change of seatpost, or dinking around with getting the measurement techniques synced up.

If I measure perpendicular to the seat tube on the S-84 I get 37 mm. Same measurement on a Thomson with setback (they do it with a bent main tube) gets about 18 mm.