I love the Sd.Kfz 251 Ausf. D, but it is not an easy weapon to wield.
Aiming is difficult. It is best to park in a field and alternate between the drivers position and the firing position to aim it. I back-turn in the opposite direction. IF the range is short, you have to turn in very small increments. This is made even more difficult if you have multiple targets and the target you want is not the first displayed.
Range is also difficult. It general seems to overshoot, but all the rockets fall at varying ranges.
Because of this, you really don't want a friendly anywhere near your target. Also it is easier to aim and shoot with longer ranges.
I look forward to the next theater when the Sd.Kfz 251 Ausf. D should really start to come into its own.