I have made about 8 T-shirt quilts. I use my 12 1/2" square ruler and cut my shirts out using that. I do not move the ruler at all. Basically I contort myself to cut out the square so I don't have to move the ruler. I don't stabalize or starch when cutting but as soon as I cut the T-shirt square I have my ironing board right behind me so the cut square goes on the ironing board and I have a 12 1/2" fusible interface ready to immediately put on my cut T-Shirt. I agree with the others, you need a bigger cutting mat too, at the very least it would make things much easier for you and result in more accurate cuts.