I have a 2000 F350 and a 2014 Lance 1191. I weighed it with and without the camper on DOT scales at a Love's station and I'm about 1300 lb's over my GVWR fully loaded with passengers. On the other hand, I'm under on my axle ratings by a few hundred pounds. I started a thread on the Lance Owners site and got the reply that the manufacturer's frequently understate GVWR in order to stay below federal and state regulations for Heavy / Commercial Vehicles. They said if I'm below on my axle ratings and comfortable / feel safe with the handling I'd be ok. The truck handles it great. My previous camper (same truck) was a 2004 Lance 1161 which was all wood frame and even heavier and it did great as well.
What are they trying to avoid by underestimating the ratings? Commercial Vehicle Registration Act of 2001 (F450). Federal Heavy Vehicle Use Tax (F450). I live in Arizona and they have a tax that the F450 falls under as well.
This also explains a mystery to me about the new trucks having increased their towing to 30K lbs+, 400/800 HP/TQ, but have only increased payload & GVWR by a small fraction. Hmmm.
To your point on the Adventurer, it would be in the weight league of my camper and I wouldn't hesitate putting it on my 2000 F350 DRW.