Seeing an "upside-down" image as natural is very natural! In fact, that is how our brain receives the image in the first place. The basic law of optics dictates that the image thrown upon our retina by the lens of our eye must be upside down and backwards...yet we perceive it as right-side up and non-reversed. So this is an exercise our brains are quite familiar with.
It is easy, at least for me -- I did not have to work hard at all to find the upside down and backwards image to be comfortable and natural way to view the scene in front of me on the GG.
This has always happened for me so fast that I never think about it. I did not comment on this thread about it because I just thought it was me. As a left handed person, I learned to do left-right reversals so I could learn to do what the teacher was doing with her hands.
Warning!! Handling a Hasselblad can be harmful to your financial well being!
Nothing beats a great piece of glass!
I leave the digital work for the urologists and proctologists.