On a JR positive expo values will soften the sticks around center... I suggest that you start with 40% on both elevator and aileron. If the plane is sluggish you can switch to high rates, land and lower the value 10% or so until you find the right setting for you... You could start at 20% and work your way up too...

Stiffer spings can also help and there are stiffer replacement springs available from JR. I got mine from Radio South -- for my Futaba 9Z WCII