The issue with FMQ using twin needles would be the relationship of the needles changes as your fabric moves from side to side.The distance between the thread paths on the fabric will be the width of the needles going front to back or back to front. It will decrease to zero as you go side to side.One thread will cover over the the other. Hence the little area between the needle paths will constantly change as you are FMQing. But then, maybe that is what you want? tim