I also had a couple herniated discs and finally had to have a spinal fusion (L5). As a result, I cannot bend my back as others do.

If I'm riding and want to get in an aerodynamic posture (as much as I can), I have to rotate my hips forward. In that position, my weight is not on the "sit bones" -in fact, my "sit bones" are barely touching the saddle. Instead, my weight is primarily on the base of the pubic bone.

That position can get uncomfortable (to say the least!) on the girly bits. The only work-around I've found is to exert more force than usual on the pedals at a lower cadence than is generally recommended (versus the "ideal" method of spinning the pedals at a fast rate with little force on the pedals).