GMC Sierra 2008 Owner's Manual page 350

Here is an example of proper truck and camper
match:
Camper Center of Gravity
A.
Recommended Center of Gravity
B.
Location Zone
When the truck is used to carry a slide-in camper,
the total cargo load of the truck consists of the
manufacturer's camper weight figure, the weight
of installed additional camper equipment not
included in the manufacturer's camper weight
figure, the weight of camper cargo, and the weight
of passengers in the camper. The total cargo
load should not exceed the truck's cargo weight
rating and the camper's center of gravity (A)
should fall within the truck's recommended
center of gravity zone (B) when installed.
4-48
You must weigh any accessories or other
equipment that you add to your vehicle. Then,
subtract this extra weight from the CWR. This extra
weight may shorten the center of gravity zone of
your vehicle. Your dealer can help you with this.
If your slide-in camper and its load weighs
less than the CWR, the center of gravity zone
for your vehicle may be larger.
Your dealer can help you make a good
vehicle-camper match and help you determine
the CWR.
After you have loaded your vehicle and camper,
drive to a weigh station and weigh the front
and rear wheels separately. This will tell you the
loads on the axles. The loads on the front and
rear axles should not be more than either of
the Gross Axle Weight Ratings (GAWR). The
total of the axle loads should not be more than
the Gross Vehicle Weight Rating (GVWR).
Open the driver's door and look at the
Certification/Tire label to find out your vehicle's
GAWRs and GVWR.
If your vehicle has gone over the weight ratings,
move or take out some things until all the
weight falls below the ratings.