It took a couple of weeks to get used to my Fizik curved saddle. Terrible at first, then "okay", then "perfect" after a month. It's slightly nose up, so that the rear portion where I sit is fairly level.

Sliding forward:
This bike fitter wants to get the saddle correct, then change the stem if necessary. Sliding the saddle forward to fix reach problems isn't the way to go.

See the balance test starting at the 4 minute mark. This was useful for me.

https://www.youtube.com/watch?v=SZhWVZq2qUc

~~~~
Okay on short or medium rides, but back pain on longer rides? Maybe just more miles will help.