The design has QUITE a bit of natural stretch due to the open lacy design!
Here are the sizes as published in the magazine:
XS/S – finished width = 32 inch bust/waist/hip unstretched, stretching easily to 34+ inches.
M/L – finished width = 39 inch bust/waist/hip unstretched, stretching easily to 41+inches.
L/XL – finished width = 45 inch bust/waist/hip unstretched, stretching easily to 47+ inches.
The pattern could be made with a category 2 weight yarn instead of the Category 1 listed in the instructions. This would of course increase the size. I haven’t worked the design in this weight yarn, but it works up quick and you’d be able to tell by right after the split for the sleeves if you’ve got it right!
To use the Category 1 weight yarn, here are the modifications you will need to make for the 2X/3X size, it’s basically just the starting Row that changes by adding 6 stitches, and then everything else follows as written.
2X/3X – finished width = 52 inch bust/waist/hip unstretched, stretching easily to 54+ inches.
I’ve included the ending stitch counts for the first several rounds just as a help. Row 1: 78 fsc
Rnd 2: 78 hdc + 78 ch-1 spaces
Rnd 3: 156 sc
Rnd 4: 26 shells
Round 5: 52 ch-3 spaces.
Round 6: 78 ch-3 spaces.
Continue as pattern indicates.