I am not familiar with the DX7 but, when comparing to other brands, most people use 20 to 50% expo. If a Futaba or Hitec it is negative expo, if JR it is positive to soften response around center stick. I would think 100% would be very hard to use as that would mean essentially no control movement near center stick with it snapping full over as you reached the end position. Do not confuse expo with dual rates as, when you say 100%, I'm inclined to think you are adjusting dual rates.