Pants are HARD!!! Here are the first and second muslins. For the third muslin, I decided to add .5" to the back crotch extension. And I changed the shape of the front crotch to something flatter and less roomy. Here is what I got.
I omitted the back yoke because it has nothing to do with the fit. The back crotch fits better, however I still have a massive pouch on the front. So perhaps I should reduce the front crotch extension....I turned my pants inside out to expose the intersecting crotch seams. Then I made a small fold on the front side of the seam and pinned. I had to do this several times to get the fold the right size.
I will measure the fold, multiply by 2, and that will be the crotch extension adjustment. I hope this is the last muslin.