I believe that the book you are referencing is one of the textbooks I had I my Hi-Po drivelines class in college. And you are right, it has a lot of valuable information. I just feel like you are misunderstanding the stored energy part. Light rate springs release their energy through a longer travel, but don't store MORE energy. The weight removed from the front of the car is based only on the power that the car is able to apply to the ground, which would be the same no matter what spring is in it. As soon as either spring is fully extended, the unsprung mass begins working against weight transfer. The lighter rate spring just allows more weight transfer before that happens
