GMC 2007 Sierra 1500 Pickup Owner's Manual page 446

The trailer tongue weight (A) should be 10 percent
to 15 percent of the total loaded trailer weight,
up to a maximum of 600 lbs (272 kg) for the
1500 or 2500 series, and up to a maximum of
750 lbs (340 kg) for the 2500 HD or 3500 series
with a weight carrying hitch. The trailer tongue
weight (A) should be 10 percent to 15 percent of
the total loaded trailer weight, up to a maximum
of 1,000 lbs (453 kg) for the 1500 series and up to
a maximum of 1,500 lbs (680 kg) for the 2500,
2500 HD or 3500 series with a weight distributing
hitch.
Fifth wheel or gooseneck kingpin weight should be
15 to 25 percent of the trailer weight up to the
maximum amount specified in the trailering chart
446
for your vehicle. See "Weight of the Trailer", and
"Fifth-Wheel and Gooseneck Trailering" in this
section.
Do not exceed the maximum allowable tongue
weight for your vehicle. Choose the shortest hitch
extension that will position the hitch ball closest
to the vehicle. This will help reduce the effect
of trailer tongue weight on the rear axle.
After you have loaded the trailer, weigh the trailer
and then the tongue separately, to see if the
weights are proper. If they are not, you may be
able to get them right by moving some items
around in the trailer.
Trailering may be limited by the vehicle's ability to
carry tongue weight. Tongue weight cannot
cause the vehicle to exceed the GVWR (Gross
Vehicle Weight Rating) or the RGAWR (Rear
Gross Axle Weight Rating). The effect of additional
weight may reduce your trailering capacity more
than the total of the additional weight.