I made up a pair of the sandbox pants in stretch uncut corduroy and my kiddo wears them All The Time. As a result of constant wear and wash, the fabric has frayed dangerously close to the narrow seam on the crotch area. This is the area where I stitched 2 stitch lines between the pattern notches then clipped 1/8 inch from the 2nd row of stitches. It's still holding but is visibly weakened. How should I reinforce this seam to prevent an embarrassing moment?!?