Maybe the knives weren't set correctly as this stuff was awful, wish I'd taken some pictures, it was some tough old grass though. I was clamping with a tractor weighing approximately 12 ton. Seems ironic that you need a similar horsepower tractor on the clamp to that of of a small sp forager, I'm sure you don't need that much power just the weight of the that size tractor.
Yes correct, 939 is hardly using any of its power hence why it can pit 200ac and the fuel tank has hardly been touched. It is its ability to push right through full 16t loads that are ejected into tight pits that means it can keep on top of the job. Once the grass is shifted a quick roll at low revs and its ready for the next load- effortless.