At one point, I went with the recommendation based on the Specialized ass-o-meter. I did not hear or see anything that took into account anything about the pubic rami, the parts of the pelvis that come forward from the ischial tuberosities.
If it's not a prostate problem, it's probably excessive pressure on your pubic nerve and/or artery. I recommend reading the Selle SMP patent application and the material on ismseat.com on the design principles of their ,,,um... device (the one that fits on a seat post which is typically inserted into the seat tube).