I am not sure yet, but I am experimenting with crank lengths to see how much influence they might have in relation to saddle position and ride comfort. I went from 175s to 170s several years ago on most of my bikes, but have reverted to 175s on the new Santana tandem. RonH hasn't mentioned anything about crank length, so I am presuming they are the same length. If not, there might be something there, too.
I know I got caught out a little when putting a new Brooks on Machka's old Giant OCR3 the other day, and took the saddle height measurement from the BB spindle rather than from the crank at BDC. The cranks were 175 compared to 170 on her other road bike. It made a significent difference to her fit.
The Brooks saddles also highlight the need to take measurements from the compression point when seated rather than unloaded (if you know what I mean). The same applies to padded saddles. I remember a woman rider who had trouble getting comfortable on a bike until she found out the foam in her favourite saddle had basically collapsed on one side and was making her ride crooked.