Simple answer is to raise the trailing edge to reduce the wing incidence, this should get rid of the down elevator trim.

However as speedracerntrixie pointed out, this may affect other areas of the flight envelope.

My F3A ship only has an adjustable stab and needed a heap of up elevator from out of the box, so I wound in a heap of negative incidence on the tailplane to get rid of most of it, which fixed some other issues it was having and created a few more that took some twiddling of the motor to sort out. Running up or down elevator trim isn't a bad thing unless it's noticably causing bad things to happen...