When I was learning to use my longarm I did put an extra piece of batting and top fabric on the side of my loaded quilt to test the stitching. Tension and speed were my main problems. Tension is something that I still test if I'm quilting unusual materials like fleece or TSHIRTs or if I change thread types. I really had to slow down for best results. After a learning time you will probably know what works best for you and which fabric/thread combos you will have to test/adjust for. Good luck & have fun!