Splitting the 4-ply worsted weight yarn into 2-ply. It takes forever!

Front:
Provisionally CO 39. Keep first and last 4 st in seedstitch, make the rest 9x1 ribbing with the center st a p.

After about 7 rows, do k2tog, YO across (be sure to end up with 39 st)

Another 7 rows or so, then join with cast-on to make casing.

Now inc one with YO both sides on RS rows, just inside seed st border. Work until you have 65 st. Make back piece the same.

Then join by casting on 15 stitches at underarms (160 total) Keep underarms in seed stitch for 5 rows, then continue k9p1 ribbing.