Best solution is get rid of that Macdon junk and get a real flex header. You said S680 so you probably don't hate John Deere so one of these would likely fit the bill. Or an Airflex.
Headers shouldn't have to "smile" or "frown". They should follow the ground.
I would be considering getting rid of combine before parting with the FD1. Makes no sense that the FD1 is not shaving the ground. Certainly not my experience here nor the many hundreds or thousands of other MD FD owners out there. They didnít get to #1 putting out bad products.
That 45' header might not have been the best choice to pick up crop on rolling land to begin with. I remember noticing quite a difference when I switched from 35' to 40' headers. The 40' just wasn't emotional enough to do a good job in the twisty stuff. It just didn't smile or frown enough.
Does anyone know how to adjust this or is it even possible? id love to steal some frown and give it to the smile.
I would apply this logic to the problem.
Since it’s spring pressure that holds the end sections of the header in a generally level position. Each time you make the header wider it requires ever increasing spring pressure force at the hinges. As a consequence if the center section doesn’t also get a required increased amount of mass added in the production, eventually the combined weight of the center section and the combine’s feeder house will be unable to overcome the spring force at the header hinges to make it smile.
It all hinges on if you need a flex header or hinged one can do your expected jobs.
With a John Deere HydraFlex Draper you would likely also need the auto lateral tilt feeder house option on your combine to match the lateral movement of that Macdon.
look on youtube and adjust the float like the video, and adj the wing balance, if you follow the book and the videos it should float like you want, should be able to lift up on any guard and it should take around 75 ftlbs to lift it if its set right