Just a reminder... Alligning the car is not done with weights. Weights are used for wheel balancing so that the car doesn't vibrate while driving.
Also, despite the fact that you car might drive straight, allignment is still recommended after a suspension tweek, because your steering wheel might be pointing straight and the car dive straight ahead, but each one ofnthe wheels might be pointing in different direction, also there is camber and caster that need to be checked. If those are not within limits then you are lookng at uneven tyre wear over the next thousand of miles you'll be driving and by the time younrealise it, you'll probably have wrecked a tyre or two. Better safe than sorry!