JK about 50 mph in reverse. I've only done that once and that was in a rental (definitely not the VX).

There actually are similarities between rotary wing aircraft and autos. While the RPM and load are much less on the VX (thus not needing VSS), things can get out of whack. If you're lifted, you may have added an out of phase angle to the drive shaft U-Joint. That can cause some odd clunks & vibrations.

CVs typically only let you know of their ailments during de-celeration so I kinda ruled that one out.

I assume that the tranny is still shifting smooth since you didn't mention it so I kinda ruled out the shift sensor.

Can you have your tire balance checked (also make sure they are all wearing evenly and have the same pressure) so we can rule that one out?