JLK- the expo thing is is not as you are visualizing it .
To get the proper control feel , is another thing.
For most seasoned flyers , a competition model needs some softening around center - using modern servos setup correctly
On older stuff we did what you are trying to do - reduce throws to make it manageable.
These older servos had a softness around center -simply because they were unresponsive around center due to electronics available
Modern stuff reponds instantly to a squeeze of the control stick-in fact on my Funtana -I can watch any surface move by simply moving the trims one click . Each succeeding click moves either way desired --all this on $35.00 servos .
So setup you model for some moderate throw - this stuff of "7 degrees UP and 8.5 degrees down" etc., is bull shat. just make moderate throws with at least 100% of servo travel (default travel). Ad in some expo -on the switches - say - 50% on aileron - 30% on elevator and 50% on rudder - now fly it - learn how it feels at different speeds - then adjust to suit.
Trying to follow some magic recipe for throws is futile- Ballpark it and go fly.