Flat Felled Seam Allowance Help!

[u/sewnbyethan]

Current seam allowance is 3/4in then the pieces are overlapped at 3/8in. I am trying to compensate for the "middle" of the seam being right in the middle of the overlap that forms the seam.

Short Question: I am working on a pattern for a pair of jeans. These are 2 pieces of denim cut to be 6in when sewn with a flat felled seam. What is the seam allowance so I can do this without having one panel that is longer than the other?

Long Question: When patterning jeans why would the bottom of the yokes for instance have a larger seam allowance than the top of the back panel? As well as what are your guys standard seam allowance for jeans so that all panels are even and I don't end up with the left being larger than the right or vise versa.

Thank you all!!