Place a st marker on either side of the two center sts in the front and back sections. A total of 4 stitch markers added. These will be called center markers. Crotch shaping is worked in two parts. First, the increases will happen right at the center point of each front and back section. Then, the crotch will be widened to form a gusset.
On next round (round 60 [60, 60, 62, 63, 66, 67]) inc every other round for a total of 20 [26, 30, 34, 38, 42, 48] rounds, as indicated below.
For the first 12 [14, 18, 22, 26, 30, 32] rounds, inc rounds are worked as follows:
*Work to one st before center marker, l1r, SM, k2, SM, l1l.* Repeat one more time.
Note that you maintain just 2 sts between the center markers for this section.