I swapped saddle to b17 and noticed something interesting. Left thigh hitting Sadldle side. Thought I was hasty installing so I dismount and get out the tools. The saddle was perfectly centered as I had alway ridden. I noticed the sore spot was on the rear rivet. I turned the seatpost cw off center and it is centered inside my thighs and feels better. I have had back problems. Pelvis might be twisted. Sitting at a cafe 20 mi from home. Rear is sore but monkeying around with the replacement saddle might have found the cause of the saddle sores?? Or I am just too old😄