RE: XB-70 EDF
Here are the settings on my XB-70:
The flighttrim is 1/8 up on the right elevon and 3/32 up on the left elevon.
Full deflection for the both right and left elevon is 1 inch up, and 3/4 inch down.
This works on my plane and is not overly sensitive. You have to test it on your plane to find out what works best for you.
As I mentioned before, I do not use dual rates or exponential, but I mostly fly it straight and level, no loops, rolls and other aerobatics.