yeah, that sounds small even for a male pelvis. maybe you need to go to a shop with a "sit-o-meter" ?
I didn't like the B17 either. I rode one for about 6 months and well, it was better than the butterfly and the MTB and the seat that came with the tandem, but i was still getting like you said, a little bruising and discomfort on the longer rides.
that's when i went back to the B67 which I had BEFORE I got into serious biking.