For the vpx just go in the trim setup and when you set the limits just reverse them. I ran into this problem myself and fought for hours with how to get indication to match direction. So if you have it set for an example at 50 for up and -50 for down set it for -50 and 50 and it will display and move correctly.
Would it be possible to invert the elevator trim indicator on the G3X? Currently the up position is in the lower portion and the down is in the upper portion. This doesn't seem intuitive.