I'm a huge fan of my nephew's high school basketball team where these shirts are worn (his name and number are on the back) as a fun way to show your support for the team but, geez, I feel like a bum when I go out wearing a shirt like that. I kept thinking of how I could change it up and that's how I went from what you see above to this.
I took a shirt that fits me the way I like and it also has a v-neck which I prefer. I put it down on top of the "big shirt" and traced it with chalk. I used tracing paper to trace the v-neckline onto the big shirt, too.
Then I took the rotary cutter and started cutting about 5/8" outside of my chalk lines. I used scissors to cut out the neck since I wasn't going through both layers of the fabric with the V.
I did the same thing around the hemline of the shirt, first sewing the tape to the inside of the shirt. Then I folded the tape to the outside of the shirt and stitched it very close to the folded edge as you can see in the picture below. When it was all sewn, I had this great neckline.
Before I sewed the side seams and shoulder seams, I marked 4 inches up from the bottom of the shirt so I could keep this area open to create my vents. I applied bias tape to the vents the same as the neckline and hemline.