Sit bone physiotherapy

Context: Been having sit bone pain (pressure) that increases depending on the volume of riding im doing. Both per ride (15 mins into my rides, unbearable by 1.5hrs), and per week. No soft tissue irritation or numbness. Sit bone pain is all around, not side specific.

Ive gotten multiple bike fits, tried many different saddles, use high quality bibs, etc. My last bike fit (1 week ago) was very high tech with pressure mapping and a program that showed the angles of my body. Current saddle had no signs of bad pressure and performed the best. I tried multiple others that showed pressure in the yellow orange and red, indicating a worse fit. Also my fit measurements were spot on, posture spot on, technique spot on.

So since everything looks as close and great as it can be, ive narrowed down my issue to being my own physiology. I have a history of a torn ACL + torn both meniscus in my right knee. After doing some research this issue could be because of tight hamstrings and other sit bone related muscles.

I am asking if anyone has any knowledge on this topic or could lead me in the right direction. My goal is to be comfortable riding for at most 4 hours at a time and doing 100k events. I dont know where to go, or if anyone knows a cycling specific physical therapist who could help with this issue.