Rather than weighing you can just measure the ride height on each side of the chassis, front and back.

This will let you know if more weight is being put on one side or the other (left/right) as well as ensuring you have your desired ride height front to back. As a result of doing this your spring collars will likely not be symmetrical because the weight in the car is not distributed symmetrically.

This method is really the same as doing corner weight for our cars since we do not have the ability to adjust ride height independent of spring pre-load. On real cars with more sophisticated coilovers this isn't an issue.