Where did you get your grandberg? Do you have to take the chain off the saw or is it a "guide" type?
It showed up in the case with a free saw I got awhile back, and it's the "guide" type. I set it with a 25 degree top plate angle and a 40 degree down angle, then adjust the depth and cutter length to just hit the working corner. I also rotate the file such that the "small" side is below the top plate. Two swipes with a sharp file and I'm on to the next cutter.