on our 2500 GMC (2004 and then 2015) I adjusted to bring the front down to slightly above unloaded. CAUTION. DO NOT drop it below unloaded on GM, you'll hit the rubber bump stops quickly and really make the ride rough.
the manual on both the 2500's said to drop it 1/2 way between loaded and unloaded.
My suggestion is to try what they recomend, then drop it to 1/2 and compare and then drop it back close to empty and see which handles best.
One issue is that on most trucks as the front rises camber changes noticeably and camber can affect how the truck handles and end up with front end "wander" that seems like trailer sway.