My van fully loaded, with both of us, with Stowaway II in swing hitch is about 7,900 lbs. The Stowaway with content adds about 350 lbs. including a load of campfire wood. I wonder which component(s) would impact the weight difference between our vans. Perhaps it is bamboo versus HDPE finish, perhaps steel versus aluminum rock& roll bed frame. We will likely never find the culprit but it is good to compare the notes.
I never felt as I needed to beef up the suspension, perhaps better shocks in strong wind conditions with semis interactions. Perhaps there is sufficient difference in passenger versus cargo van suspensions explaining good behavior of my van ranging in weight from 7,150 lbs. completely dry to 7,900 lbs. fully loaded van.