drmopar wrote:
Rent a water bladder to fit inside your bed. At 4000 pounds, it is about 475 gallons. Purchase a cheap gallon meter with hose adapters. Get the weight of camper, fill your bladder to match weight, and see how it works. Lot less Liability for you and dealer. Cheap test drive. At my RV-Boat storage facility we often have done this for customers.
I have loaded 4000lbs of gravel and dirt in the back of my truck many times. The ride is very different then having my camper loaded. It is not just about the weight it is ho it is distributed front to back side to side and mostly ho much higher the center of gravity is.