See revised notes 7/10 here. for 54 st cast-on.

Revised 3/10:
Toe-up Cast-on (magic loop) 12 sts, inc eor to 56 (28/28), work 2 inches from beg; start Ripple Rib on instep sts only:

Row 1 and odd rows: (K6, P1), rep 4 times
Row 2: (K4, K2tog, K 1st st again (RT), P1), rep
Row 4: (K3, RT, K1, P1), rep
Row 6: (K2, RT, K2, P1), rep
Row 8: (K1, RT, K3, P1), rep
Row 10: (RT, K4, P1), rep

Start gusset incs at 5.5” from toe tip; inc each side eor 12 times (+24 sts = 52 sts on sole needle). (Divide 16, marker, 20, marker, 16.)

Heel turn: Set aside 16 sts on each side for edge sts, work on center 20 sts for heel flap. K to last st, w&t, purl to last st, w&t, continue until you have 7 wrapped sts on each side and 6 unwrapped sts remain in the center. Right side facing: K to end, picking up wraps with each st, inc’g four evenly; with last st, K3tog (the K st, the wrap, and the first st from edge sts. Turn, Sl 1, purl back, picking up wraps on other side, inc’g four evenly; with last st, P3tog (P st, wrap, and first st from edge sts). Turn (rt side facing).

Heel Flap: Sl 1, K1, work Heel Stitch (Sl1, K1) across; at end of row, knit last st tog with first st of edge sts. Turn, Sl 1; purl across; at end of row, purl last st tog with first st of edge sts on other side. Continue until heel flap is finished and edge sts are joined, ready to resume working in round on pattern sts on instep.

1/12/09: started second pair, also with Sock Hop, “Riders on the Storm”
3/12/10: finished third pair, “Good Vibrations” green