I run mine without any differential, It is a single servo setup however, so putting in differential would be hard. I really don't think you would notice a difference because this is not a smooth flying pattern plane. It is screaming all out fun.

The only thing I remember about differential is that if you mount the servo on the bottom of the wing (like the hellraiser) to improve the differential you could use a V arm on the servo. The bottom of the V would be toward the back of the plane. I tried
to figure out if that causes more up than down, but I am afraid I not able without running an experiment.

Larry