I have used denim jeans as cornerstones in T-shirt quilts and regular cotton fabric for the sashing. I always use a fusible interface to stabilize the T shirt material.
Here is link to one I did double sided. The front I did the shadow box with regular cotton and the back I did sashing and cornerstones and used some of the denim for the outside cornerstones. I had no issues and I have done several like this.
Double sided T-Shirt quilt