First of all, an ARF probably has the wing saddle pre-cut and it is what it is. You could use the incidence meter to see if the wings are straight. Just mount the wing and check that the angle shown on the meter is the same on both sides of the plane. Mount the incidence meter at the wing root on both side and compare the number, it should be the same. Then mount the meter at the wing tips and the two reading should be the same. If angle numbers are given for your arf between the wing and tail, you can measure the angle at the wing and then the tail and see if the difference equals the number you are looling for.