Hey, I'm from Boissevain. We ran the rigid Mac-dons (the D60-D) this past year and loved them. As far as combine setup it didn't take much, hopefully you ordered the Xtra high capacity lift cylinders they can lift the header in low idle without even a hesitation. Our old 9860s had a tough time with a honey bee header of similar weight. I went against what everyone told me and I tilted the combine feedhouse all the way forward, then used the hyd header tilt to fine tune for cereals/peas. It worked out fantastic, with the header tilted almost all the way forward we picked up one of our flattest pea crops at 5-5.5mph (the peas were about 3" tall in some spots) Then I tilted the header back for cereals and hardly ever picked up a rock, the guards on the header were actually pointing upwards a bit.
Getting the headers level was a bit of a project, but not hard once you understand what needs to be done. When they were in the air they were perfectly level sitting down on the stops, if they are not level at this point there is a large nut that has to be turned on each side. We lowered them to cutting position and they didn't want to follow the ground level so then this was a matter of loosening/tightening the springs on each side.
I believe there is just a lever that makes the FD70 go from flex to rigid and when in rigid it would work like a D60. They are a fantastic header in cereals with heavy straw, hardly ever plug up, but when they do they have a nifty feature when you reverse them the reel reverses as well so no more picking straw out of the front of the combine. We had them on our combines in 80bus Soft white wheat, heavy straw, around 4.5-5mph and it was never and issue. Even had a Demo 9120 with a 40ft Macdon in the same field doing 5.5-6mph and no feeding issues either.
Something to consider, the new 70 series chopper is better than the 60 series but I don't believe that it is as good as a 9860 premium. It doesn't spread the full 40ft with the regular tailboard so we got the powercast tailboard and now it spreads 50ft.