I've mentioned this a couple of times in the past.
I fixed this with a magnifying glass. It's a little involved but much much less so than dismantling the speedo.
Connect the speedo cable bottom end to a variable speed drill that you can set the speed on (little adjustment screw on the trigger. most cordless lack this.)
Run the speedo up enough to take the needle off of its rest and stay somewhat steady. rock steady is not necessary. Aim the hot dot from the sun through a magnifying glass back and forth slowly across the middle of the needle till it juuuuuuuuust starts to droop downward. Careful. Overdoing it can't be corrected easily.
Worked fine for me.