if you don't want to applique the t-shirts to the centers after assembling as instructed, let's try looking at it this way:
use this link and scroll down to Block Assemply
http://www.mccallsquilting.com/patte....html?idx=8480
number the sections
1 2 3
4 5 6
7 8 9
assemble all the sub sections as pictured except leaving off the left side of 4 and the right side of 6.
it would probably be best now to layout the entire quilt on a large design wall or the floor. now, you'll have to insert the t-shirt sections into the blank spots left by 4 and 6. now, you'll have to sew it all together as you will.
hope there are no flaws in my thinking.