My model is the TDI 190cv 4x4 Kombi, GM and AL are a bit softer than those that correspond to me (GN and M) right now I have the raised suspension for bad roads (PPD) and I have HS and AS, they are quite harder than the standard ones but the car is a pirate ship from what it moves. If you are going to pull a caravan maybe you should put an N, I do not think that the difference in hardness is critical in any case and it is almost better to go too hard, since very soft will make the car sink with its own weight.
If you want something harder, the next combination is GN and M and the following GP and P. Here you decide. If when they install mine it is soft, I will go for the following configuration that I tell you.