I just did a test. I only shoot in PRO, the one I did 2x, it is really 2x in.
From what I read, the 2x is actually in 50MP and the camera zoom in to the middle part. I have look at it and it is very useable and good result, just a very slight...
Take a medium exposure. Then slide the EV in your photo editor to make all your brackets. I have made up to 2 stop up and down and I get all the information I want. You must do this in DNG.