It is essentially the original t-shirt without sleeves.
I made it in plain black, and checked the fit and left it unfinished.
But then I had a bit of this left over.
I cut strips of the leftover piece parallel to the stripes. A bit of playing about and I decided I wanted the strips about 3cm wide. This allows a 1cm seam allowance, and an exposed strip of 5mm. I chose 5mm because of the size of the stripes - if the stripes were wider, I would have made a wider strip. I was aiming for the effect of little squares - a broken dashed line around the edge, since the black lines should blend with the black fabric.
I cut the neckline strip about 5/6 of the length of the neckline - perhaps a little larger since there isn't as much stretch in the fabric in this direction. I cut the sleeve strips almost exactly the same length as the edge, since I don't want it to pull in snugly around the arm. I sewed them on, clipped the curves and then top stitched. When I got to the arm I had a brain wave, and just clipped the two in between layers so that the top edge would stretch over and make a prettier finish on the inside. I don't know how well it would work on the neck edge as it has to curve much more dramatically, but I'll try it next time.
This is the resulting edge.