I am in a similar process of setting my MTB up for a jaunt on the GAP-C&O Trail. I also opted for the B-17 which isn't compatible with the SDG I beam clamped seatpost that came on my Cdale. The Brooks is a classic looking piece of retro style. I'm trully more interested in how much relief it can provide to my classic backside over a 4 day 335 mile +- ride.
The man in the little brown truck dropped off a Thomson Elite Layback yesterday that is supposed to give up to 1" more rearward adjustment. After a rough look at the two together everything seems to be compatible.
I'll be mounting the saddle this evening and plan on starting the break-in tomorrow. I should be able to give you an assessment after that if you would like.