My distance scale window for the 400mm f2.8 VR is cracked. Having a difficult time finding the part online.

How does the 400mm f2.8 VR handle the 2x teleconverter?

The modern Z lenses aren't built to the same standards as any of the f-mount 400mm f2.8 versions, in my opinion. The newer lenses are lighter and possibly handle flaring marginally better. To me, it's not worth the price difference until they start showing up on the used market.

How does this lens compare to more modern Z options like the newer s-line 400mm f2.8 or the 400mm f4.5?