The secret to t-shirt quilts is to iron on the fusible interfacing FIRST, before you cut. That takes care of the stretching problems. I made one for my stepson. I went to the local glass shop and asked them to cut me a 16" piece of plexiglass, they did, no problem (cheap too). I laid the template on the interfaced t-shirt and zip-zap I had nice squares, all the same size. I did sash them but only because I thought it needed color.