I'm a 'new' Brooks fan. Accepted a bunch of others (over the past couple decades) on my various bikes, but tried a B17 Flyer S a couple years ago on my daily commuter. I now have a B17 Flyer S on my commuter, a B17 Flyer S on my road bike, and a B17 on our tandem (captain's position).

I get the same pain you have when doing long trips on the tandem. I think it is the seat size/length....I'm only 5' 7", and the S versions of the Brooks seem to disappear under me. I'll be getting another S version for our tandem. Maybe that's the issue with the B67 (it's too big for long distances).

Whatever saddle you end up with...if you don't go for a proper fitting, dedicate a couple 4-5 hour rides on it, and keep the saddle adjustment tools (whatever you require) in your back jersey pocket. I literally adjusted my first Brooks so much I got tired of stopping, but eventually it 'just disappeared' and was comfortable.

Maybe try a retailer who offers a longer term return program. Like wallbike.com (I'm only a happy customer, not affiliated).

HTH. A lot of other good suggestions!