The single best improvement I made (as far as rear visibility is concerned) is to remove the rear seat headrests.
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Most of people that ride in the back seat refuse to remove their heads, so this is still an issue when someone is riding in the back. Then, I decided at one point to only drive forward. This worked for nine days - until I was forced to drive into a one way dead-end alley. The VX then sat in this spot for over three weeks - until I finally yrealized it would be necessary to drive in reverse.
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Seriously ....... remove the rear seat headrests ........ and see if this makes a difference ....

I (also) applied the fresnel lense - VanEyes - VanGuard (VanGard ?) - whatever - to the rear window. I purchased the 8x11 size and applied a 4X11 piece (modified with a half moon cutout so it will sit directly over the sparetire hump) on the 'middle bottom' portion of the rear window. The lense will allow you to see something that is directly behind you. It does make distant objects appear *very* distant however.
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Someday I may apply the small (convex ?) mirrors to the sideview mirrors. I have noted that some prefer to apply them to the inside of the mirror - close to the window - while other mount them on the outside part of the mirror. ???