Re-pinned to remind myself that I have a couple of huge shirts that this might work well on! Braided neck t-shirt -it makes the neck of the shirt much smaller. Do this with a shirt that is huge on you and then you will be happy with it. All of my small women's shirts turned into tunic dresses for Lilli!
weaving t-shirt back (or other parts), for "air conditioning" or just for the look...could do easier but less exact way by cutting slots across t-shirt in one direction, then sewing a strip of long strips from another fabric or t-shirt at end of other direction and weave them through the original strips (and tack down at other end)