I would not characterize the factory backseat ride quality as "well."

Kids probably weigh 70 lbs with their car seats, dog's another 40 lbs., roof basket is 40 lbs., spare tire/rim is probably pushing 60 lbs., rear cargo carrier weighs 150 lbs. unloaded, then another 100+ lbs. in the carrier itself. With all that weight I'd be permanently riding on the stops/helpers which is surely not their intended purpose.

I need stiffer springs or a supplemental system of some kind.