Everybody is doing to be different, but with perenium problems, I'd be looking at the width of the cutout, and support of your sit bones.
There used to be a blog post by Cervelo called, "The four and a half rules of saddle fit," or something very similar - see if you can find an archived copy somewhere.
Basically: correct width (get measured), not too cushy, flattish... something else
... and a cutout if necessary (it likely is in your case).
I've had similar numbness issues on the trainer. I got my sit bone width measured (any bike shop that carries Specialized should have an ass-o-meter) and found that I needed a wider than typical saddle ~155mm or thereabouts. The saddle profile also has to be relatively flat from side to side - I needed to support the structure, not have a saddle that wedged in to soft tissue.
I also needed a wide cutout. For my personal needs, I've found that Shimano/PRO Stealth saddles in the 150+ size work well.