I have an f540 it is a great header in as far as the flex goes. When doing cereals, it is a little less than great. I have trouble with the straw wrapping around the auger then plugging the header. Probably the worst part is the jd can keep up. Tried the maxflow and awsome in cereals but not so good on the ground. A 40' rigid just doesn't work for me, and sometimes it can be 25% of our crop. so back to the fd70.