I had the SI Diva and found the cutout too wide (and too long) which put pressure and caused numbness - not on my girly bits - but on the area next to them. If I understand your description correctly it is the same area that you are having trouble with.
For me the SI Lady (LDY) Gel flow turned out to be THE saddle for me. I now have it on all of my bikes including my mountain bike. For me it is the perfect combination of cutout size (both length and width), nose length, and width in the back of the saddle. It has a quite different shape from the Diva - some have said it is similar to the Terry Butterfly but they didn't seem THAT similar when I visually compared the two. Probably one, or both, of the designs have changed.
Do you have a LBS that would allow you to demo the Ldy Gel Flow before committing to it? I was fortunate to find one, which is nice as they aren't cheap...