Red long-sleeved shirt
Black-long sleeved shirt
Establish the center front. Fold the shirt in half down the front, matching the armholes and side seams. Iron along the center front fold to create a press line.
Remove the neck ribbing, sleeve cuffs and sleeves using a seam ripper. These will most likely be serged together, so be patient.
Cut the shirt body in half along the press line.
When putting the shirts back together use a stretch stitch like zigzag or triple stitch. You may find it easier to put the sleeves on to split the shirt seams down the sides as well. It would make it easier to sew the sleeves back on and then you could stitch the sides back. Start at the sleeve opening and stitch down to the underarm and then down the side in one continuous seam. Use the smallest seam allowance you can to sew the two sides of the shirt body together so that you don't change the size of the neck opening too much.
When applying the neck ribbing, stretch it to fit the neck opening while you sew. Mark the ribbing in fourths and then match these marks to the center front, center back and shoulder seams. That way the stretch is even across the neck opening.
There is no sleeve ribbing on the shirt so just fold under and hem with a stretch stitch.
Joanna's pattern was taken with permission from home.earthlink.net.