I rather think of it like this:
For most of the times, it's not appropriate to put any penalty Kubb behind the King, and when it is not, it is pretty easy and obvious to tell where to put it.
Then, we have the opportunities, when to put it behind the King?
If the general conditions are bad, for me this will be a strong indicator it might be profitable. If the wind is strong and tricky, if it's cold or/and wet, are some factors making me concider this place. Playing tournaments in bad weather conditions have given me this experience. I've seen good players hit the King, not beeing able to tell if it was a bad shot, or did the wind took the baton, or did it stuck in the hand because of all water, or was the grip around the baton hard for him because of cold and stiff fingers?
If I want the opponents to waist a stick or two before heading to another penalty Kubb where I feel comfortable with the distance, is another factor. If you place a penalty kubb just for the purpose of having the opponents to waist at least one, preferably two, batons, then I will concider this option.
A third factor is if the opponent, most likely to be the one to take the penalty Kubb out, throws with a larger angle on the baton when throwing. Then, as well, this could be a useful place to put a penalty Kubb.
The fourth factor is of course the over all standard of the opponents. Meeting rookies, I will also concider this option.