Patching t-shirts

[ggmum]

Kind of a quilting question. I'm making my dd a patchwork beanbag out of old clothes. i want to patch t-shirts for the top. Would it be better to iron on some stiffening to the back of the t-shirts before I sew them together? Or would they be ok as they are? My thoughts were that they would be too stretchy for a bean bag as they are. The pattern I am using is a circular top and bottom and a welt. The sides are mainly lightweight denims. If the t-shirt thing works I plan on making a full bedspread.
Thanks.

[Antidigger]

If you want to use them for the base, I'd stiffen them, but maybe not for the top, since the sides are denim and will help keep the structure.

[Eamea]

I would iron interfacing to the back of the T shirts.  Even if you only use the lightweight webbing it will provide some structure and pull/pucker less.

[Stifflersmom]

I agree with the interfacing idea. Nothing worse than stretchy bunchy puckery seams.