I'm also hesitant to recommend a 2-sided t-shirt quilt. Getting the top and backing aligned will be difficult, as someone else has pointed out, and being able to see where you are quilting will be difficult. Some tees have thick rubbery printing or pictures on them, and I find it's best just to avoid quilting those areas. If the shirts on the back have this kind of printing, you might find yourself tearing your hair out.