Ok...here's the Spoileron mixing rates I'm running on my JR DSX9:
Flap Switch Pos Up - Ale 0% Ele 0% (normal flying)
Flap Switch Pos Middle - Ale 20% up Ele 4% down
Flap Switch Pos Down - Ale 80% up Ele 20% down
I don't tend to actually use the middle position on the flap switch, just the fully down pozzie for 80/20 and it seems to land nicely.
Remember, this is on a JR - YMMV
Oh, and I also run a 1/2 second delay deployment of the Spoilerons (both ailerons go up, as opposed to 'flapperons' where both ailerons go down, and the elevator goes down to compensate for the nose lifting when the ailerons go up).