I use a B66S which is the same saddle as the B67 but uses the proprietary Brooks clamp which required me to get a new seatpost when I swapped it onto my current bike. I like the springs, it’s the only suspension on my bike, took a few goes to get the seat angle right for me. Not felt the need to use proofide in 2 years of use.
This photo is a bit crap but shows the saddle angle. Apologies for the rather busy seatpost which has a weehoo attachment point over an additional QR clamp on the seatpost required to raise the weehoo bar to clear the rear rack.