Good news, you can use the FX9’s viewfinder assembly on the FX6. Not just the loupe/magnifier, but the entire viewfinder including the LCD. It all fits straight on to the FX6 and is full functional. Overlays, menus and the touch screen are all good. The only small thing is the display is initially upside down, but that is easily resolved using the “rotate” switch that is at the bottom of the FX9’s LCD screen.
So – if you have an FX9 and an FX6 you can swap viewfinders between both cameras. We already know that if you simply add the loupe/magnifier from the FX9 to the FX6’s LCD that it fits, but tends to be a bit “droopy” because of the weak hinges on the FX6 LCD. You can buy the FX9 LCD as a spare part along with the loupe if you want, but it won’t be cheap!