[unruhjonny]

I wanted to reply earlier, but stayed quiet incase my recollections might have steered wrong;
It was your mentioning of different blade lengths which made me take pause.

Now, I have only had non-recessed wiper cars;
Although recessed wipers were optional for base & Formula models, they only came standard with the Esprit and Trans Am models.

My wiper blades are the OEM trico blades in the original brushed metal housings;
Mine measure in at roughly 18"

I do believe that if you have removed your wiper arms at any time, they need to be reinstalled with the arms at the "rest" position - I have understood that people have messed their situation up by re-installing arms with the armature(?) not in the "rest" position - or by trying to set down the arm to make a non-recessed wiper appear to be a recessed wiper.