There are two narratives to adding weight to a racer car:
- You add or remove weight to just change classes without caring about the effect on the suspension and percentage of rise.
- You add or remove weight to change classes, from specific locations, knowing how it will affect the suspension and percentage of rise.
As others stated, if you ever have an opportunity, scale the car and check the instant center and variations by placing weight for different classes at various locations and document your findings.