Thank you so much for your replies.
I haven't come across the SMP or Moon saddles, but I'm taking a note to do some research.
To clarify: The pain/numbness is still in the perineum, not the sit bones.
I forgot to mention that I got epididymitis as a result of that route two years ago, and I'm sure that's the pain that's coming back when I cycle (nothing else triggers it).
Cheers.