A few years ago I switched to those unitstrut type wipers. You know the ones without any support struts, just a plastic arm holding the squeegee. First one I got were Michelin branded and you know they didn't work very well for me. Didn't wipe as well as I thought they would. My friend had Bosch branded ones that work very well so I tried that brand. There are a few different versions and I don't think I got what he has. Anyway, these were no better. The passenger side especially, there would be a patch of the glass that wouldn't get wiped. This patch was under the path of the wiper directly beneath where the wiper attaches to the arm.

Oh I tried all the tweaks. And all the glass cleaning methods. Still no joy.

But the other day I decided to take more drastic action and tweak the amount of downforce the arm has on the glass. I took the spring out of the arm and the C shaped bit of wire that connects the spring to the part of the arm that attaches to the splined shaft.

I shortened the effective length of the C shaped bit of wire from 36mm to 33mm by squeezing it in the vise. 

When all back together the arm had more downforce on the glass and the squeegee of the wiper made full contact on the glass and the wipers worked perfectly .

I think you could over do this and have too much force, and this make the wiper motor and linkage work too hard. Just a little shortening of the C shaped wire was enough.

I have to ink other people have discovered this. And I have to think that over time the C shaped bit of wire is stretched and also that the wiper spring loses some of its oomph.

Alistair