Hi.
Brooks act like a hammock. The rails bend in and up when you hit a bump. If there isn't enough rail on one side, it can't bend, and the saddle will often feel hard. When I shoved a B17 back, it felt like a rock up front. Not good. So now I try to clamp the saddle rails close to the middle. Forward seems to have less of an effect than sliding it back. The 'tricky' part with moderne frames is finding a seatpost that can pull that off. Sometimes this means a lot of set back. Triathletes have this adapter that gives you extra set back from a standard post.

Any porous material like cloth or leather will draw water up. So if spray is just hitting the bottom edge, it could still draw the water
into the main part of the saddle. At least that what my paranoia tells me
So I get lots of Proofide on the edge of the saddle. I'm not really sure if that's a problem, or if what I'm doing is the best solution. It's just what I do.