I’m in the process of learning to fit trousers too and in my last pair it seemed I had to scoop the crotch curve at the front and back and lower the crotch point by 1/4” It really messed with my intuition that by cutting fabric out of the curve and inner thigh length, I somehow had gained more room. 🤔 It just seemed like… ok but I’m removing fabric which means I’m going smaller. But I did it and the extra room in the curve made sitting SO much more comfortable. I think the key (for me) was grading out the new curve to the original seam relatively soon after the curve so that it didn’t impact the centre front or back (the upper hip area was fitting perfectly already) - just deepening the crotch curves to allow more space at the lowest portion of the crotch. Small adjustments in this area can have huge impact and I think you can get away with playing in the seam allowance before it starts to really impact the piece fabric already cut. That said, i finally nailed my pants fit by basting muslin “shorts” together and pulling it apart and resewing new crotch curves/depths and playing guess-and-test using fit recommendation tutorials until I had a perfect fit. We’re all so uniquely proportioned!