As a 3D hooligan I use expo on any size of 3D model. When you have big movements of large flying surfaces it helps a lot to use the expo to reduce the amount the surface moves compared to the stick movement around neutral.
On a trainer you will not notice the effect of expoin fact you may not want it.
But on this indoor 17 inch span monster with 45 degree movements on all surfaces you want lots of expo. I would use about +60% on a Futaba set.