Hope this makes sense! My trick is to use the flat of my hands to evenly distribute the excess fabric as I stitch the seam. If I lay both hands flat on the quilt, one on each side of the needle, gently pull hands apart while holding the fabric and let the machine pull the quilt through. By pulling the quilt taut like this, the excess fabric is evenly spread out over the length of my hands and the fabric that might have made a visible tuck at the next cross seam is evenly distributed across the area under my hands.