I feel it would be ideal if after you and your family are riding down the road all loaded up with people, gear, food, water and fuels, that the rig would have 500-750 pounds of extra margin per axle. Less than that seems too close a call. More than that and you'll be getting a rougher ride.
The Sprinter chassis achieves this. The GVWR is 1,130 pounds less than the sum of the GAWRs. AFAIK it's the only Class C you can load to GVWR without busting either of the GAWRs. Tire-wise, at full inflation, the front tires can carry 950 pounds over GAWR, and the rear tires 2160 pounds over GAWR. When I'm loaded 150 pounds over GVWR, I'm 560 pounds under GAWR on the front, and 420 pounds under on the rear. Left-right balance is close to perfect, which will of course vary from rig-to-rig.
