I had exactly this problem with the B17, in the same spot (the "adductor insertion into the inferior pubic ramus", according to my lady chiropractor, who checked me out when the area was still red and tender).

I don't know my measurements but after some trial and error found that the B68 is perfect on my mixte (upright position) whereas the Swallow is *BLISS* on my Surly Pacer (roadbike).

Good luck!