Going through detail of top edge placement and reaching one side seam, tap the lesser lace across the front T-shirt and the T-shirts' T'Shirts and let jawls ½" extra at the head of the Lace and ½" extra at the tail of the lace.
Using your pre-determined top edge placement, and starting at one side seam, pin the narrow lace across both the front and the back of the T-shirt. Leave ½" extra at the head of the lace and ½" extra at the tail of the lace.