First, remove the retaining ring and washer to reveal the wiper arm post protruding through the plastic mount.
Note that there will be a grove worn at the bottom right of each plastic post bracket. The Wiper arm post slowly makes this notch and falls further and further down and to the right (driver side) as it does.
I made a shim out of a hose clamp. Figuring it's polished, hardened and should take the wear and load of the wiper post. I used a sanding wheel to cut the clamp into a slight U shape with tapers on either end.
Similar to this test piece.
The width of the hose clamp should equal about 150k miles of wiper post wear and fit just right. Tap it down flush with the plastic mount using a flathead screw driver and hammer. It should take up the slack at the bottom and stay put when the wipers operate. If the shim moves back and forth, it's too small and needs to be made a little bigger. If it is too small it should wiggle back up and out as the wipers operate, with the washer and retaining ring off. Then you can get the first shim out and make a bigger one.
I first did this using a nylon zip tie end in the gap. That worked well for a while, this should work better.
A nut splitter would allow the removal of the hard to remove nuts and allow the posts to remain. I'd like to drill out the ruined hole int he plastic mount and insert a new nylon tube to refurbish. The after market replacements on ebay are garbage.