Progress!!!
Okay, so I did my muslin, adjusted the armholes, and have sewed up the fashion fabric pieces and gave it a test fit (no pics unfortunately).
Now, I did mess up the front pieces slightly because I accidentally flatlined the two front pieces the same way.
Twice.
So I tried really hard to seam rip them apart and serge it again trying to minimize the amount of fabric I lost, and I think for the most part it worked out well.
However, it kinda feels like there is still a bit of a fitting issue. First, the armholes were tight...but I haven't clipped them (apparently I'm not supposed to clip the seam allowance if I'm adding sleeves?) so I'm sure that's part of it. Additionally, it looked like there was a bit of stress going from the bust to the shoulder, which I think means it's a bit too tight there? So I think I should let out the shoulder seam a bit?
Also, I'm not entirely certain I sewed the front seam correctly, specifically at the top. I wasn't sure if I was supposed to just go straight up and the seam would intersect the edge of the fabric as it curved, or if I was supposed to curve with the fabric slightly and meet the edge of the fabric at the line. It kinda looked like it was a bit 'full' at the top of the side seam.
Hopefully this made sense without pics (getting the wife to help me when she wants to go to bed, I figured I was pushing it going for pics).
Thanks in advance.