Back: Cast on with waste yarn and work in entrelac pattern as described below.
With size 10 needles and waste yarn, CO 40 (48, 56, 64) sts. Knit 1 row. Change to working yarn and purl 1 row.
Second Tier of Blocks: change to size 7 needles. Remain on size 7 needles until the Top Triangles.
Top Triangles:
Repeat the set up row and rows 1-14, 4(5, 6, 7) more times. (40, 48, 56, 64 sts)
Back continued: double the number of stitches in the first row and then work in ribbing as follows:
Increase row (WS): *Kfb, (knit into back of wrap, purl wrapped stitch) 7X*; repeat to end of row. (80, 96, 112, 128 sts)
Work in K1, P1 rib for 4 in.
Slip live sts from CO edge onto long size 10 circular needle, remove waste yarn. (40, 48, 56, 64 sts)
With RS facing, attach yarn, Kfb every stitch (along the CO edge). Work K1, P1 rib for 1(1, 1.5, 1.5) in, ending on a WS row. (80, 96, 112, 128 sts)
Rnd 1: Work K1, P1 rib as established, CO 6 (8, 14, 14) sts for underarm, join and work K1, P1 rib across lower back sts, CO 6 (8, 14, 14) sts for underarm, PM and join work in the round. Work in K1, P1 rib for 1in. (172, 208, 252, 284 sts)
Increase rnd: *RLI; Pfb*, repeat increasing in every stitch to marker. (344, 416, 504, 568 sts)
Continue working in K2, P2 rib as established for 5(6, 7, 8) in.
Increase rnd: *K1, M1, K1, P2* repeat to end of round. (430, 520, 630, 710 sts)
Continue working in K3, P2 rib as established for 3(3, 4, 5) in.
BO loosely as follows: K2, *Sl2 sts back to LH needle, K2tog tbl, K1* repeat to end of round.