I have made many, many T-shirt quilts over the years and always used the featherweight interfacing. The quilts were always soft and cuddly. Even double sided T-shirt quilts. They are heavy but that is because the knit jersey is heavy. Lift up a garbage bag full of T-shirts and then lift up a bolt of featherweight fusible interfacing, the added weight is negligible. Now I do know some interfaces are quite heavy like the nylon tricot ones. But the featherweight stuff is indeed as light as a feather and adds absolutely no stiffness, it simply keeps the T-shirts from stretching out of shape as you sew them. I would not attempt making one without some sort of interfacing unless I starched the shirts so heavily they would be like card stock. As the starch washes out, that is a viable alternative but I have never actually tried it.