I used Selle Anatomicas for a while and found the same ever-shifting tension-of-saddle-material problem. I have also tried a Rivet, which my rando husband loves. They are super hard but very chafe-free (I'm sure there's something wrong with that spelling but you know what I mean). Too hard for me, though. My best solution, just fyi, has been a Selle Italia Lady Gel Flow. And for me, it's always about reducing soft tissue discomfort. Will be interested to hear from other Rivet users.
"My predominant feeling is one of gratitude. I have loved and been loved;I have been given much and I have given something in return...Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and an adventure." O. Sacks