I have done several tshirt quilts and the batting will determine how close the quilting must be. If you use a batting that has 4 to 6 inch quilting, then you will need to quilt inside the tshirt pieces. When I quilted mine, I did a grid of diagonal lines about 4 inches apart. Since most of tees were white, I used white thread. I also used the walking foot to go over the rubbery parts of the tees. I tried fmq, but with limited success due to thread breakage in the logo areas....no problem with straightline quilting. The white thread blends right in, you just don't notice it in the tees either.