Do you have a walking foot --even feed foot? This makes your top & bottom layers feed thru the needle evenly. It really makes a difference. And maybe you can loosen the pressure on your presser foot? I line up some reference point on my foot with a like point on the quilt and just try to keep my needle in the seam ditch..and go a little slower than usual. Work a few inches at a time so you can keep the excess quilt sandwich under control. Personaly, I'd rather just do the random quilting and not have to worry about my lines being perfect.