I have found that most of the machines come out of the factory with the rotor and cage not set-up properly. You can index the machine and then after a few hours find that it is no longer indexed. The rotor cage tends to take a "set" after a few hours and then remains pretty stable. In addition, the concave indicator does not mean anything, it is only a "relative" indicator of the concave-to-rasp bar distance. I index the concave to the rotor so it is parallel and equal distance from front to rear and left to right with the concave drawn-up tight. These measurement positions are shown in the Operator's manual from about the 7th concave bar on the left side and the 8th bar down on the right side. By that I mean, I find the highest rasp bar and adjust the concave up until it just touches and then back it off to just clear. Then I remove the indicator plate and elongate the holes to allow a true Zero indication. Then when you pull the concave up in tough threshing conditions, it really is tight. Also, I run the cylinder as fast as I can until I get grain cracking and then back it down 20-50 rpm's or if straw damage is too great, then slow it down to get all of the heads threshed with the minimal straw damage necessary. I have also found that the 8780 often does not feed properly off of the head. This causes "wads" of material to go through the rotor. Sometimes you will hear the rumbling, and sometimes you will not. These wads carry the heads through the machine unthreshed. This can often be rectified by increasing the header auger speed about 8-15%. This allows smaller "bites" to be fed to the rotor and it then does a better job. We have found that opening the bottom sieve and closing down the top sieve, and turning up the fan speed is a better way to go. This allows more air to go through the top sieve and keep material suspended in the air better, thus increasing our capacity.