Manufacturers shy to give weight info, even they are forced to do so by law, but generally 4000 lb campers are those with 11 foot length, while from 9.5 footer you can expect closer to 2500lb.
More important COG on short camper will spread the weight on both axles, while with longer camper almost all the weight lands on rear axle, meaning no go without dually.
That if you find factory rating, take it with big grain of salt as all the reports say the weight is always underestimated.