I think it would be better to change the properties of the Set Constraint Reference Orientation node so they make more sense.
(https://docs.unrealengine.com/latest/INT/BlueprintAPI/Physics/Components/PhysicsConstraint/SetConstraintRef-/index.html)
The node should take a rotator instead of two vectors and feed the rotator’s forward and right axes to the constraint under the hood. (Or whatever pri and sec axes supposed to be.)