I had been riding on a Selle Italia Flite on my F8 without issue for about a year. For some unknown reason I started to develop perineal pain. Even though it has a cutout I concluded it didn't extend far enough to the nose of the saddle. I replaced it with a Sele Smp Glider Carbon Rail. I've been on it for a little over two months with rides up to 75 miles and so far I love it. Wider longer channel and the nose down tilt feels nice in the drops.
I have a fi'zi:k Arione on my TCR which I will most likely leave as is.