Change to larger needles and proceed in stocking st inc 1 st each
end of needle on 5th and following 4th rows to 58 (66-62) sts and
then on following 6th rows to 78 (84-84) sts.
Cont even until work from beg measures 20½ (21-21½) ins [52
(53.5-54.5) cm], ending with RS facing for next row.
Shape top: Cast off 11 (12-12) sts beg next 6 rows. Cast off rem
12 sts.
Also, since the pattern doesn’t mention what type of increase to use, is there one that’s best suited for the sleeves?
I usually kfb for sleeve edges since they’ll be seamed, or you can do a M1 increase one stitch in.
Increase at each end on rows 5, 9, 13, 17 (every fourth row) until you have the number of stitches for your size. Then continue to increase every 6th row until you have the right number of stitches.
Continue knitting on those stitches until it’s the right length, then you’ll be binding off 6 stitches at the beginning of every row until you have 12 which you will bind off.
You’ve got it! Don’t be surprised if there’s not too much ‘knitting even’ to do. I’ve found that I rarely have to continue much after the increases.