Sometimes you get those projects where you are nearing the end. You go to try it on and…crap! It’s not the way it should be. Maybe you are on the borderline of needing an FBA and it turns out for the Tonic Tshirt, you should have done one. No time to recut and remake? Here is a semi-fix. It will eliminate the folded lines across the back.
Once the side seams are joined together figure out the depth of the folded amount that appears across your back. Take out the side seam and remove that total amount straight across the bottom hem. Sew the side seams back up by matching the bottom hems first. Stretch the rest of the back above the waist notch, to fit the front side seam. Sew back together.
This isn’t the ultimate fix for this problem, but it can help save a project from the loser pile.