[RMcNeal]

Did you weigh the truck without the camper attached? The critical part is the pin weight, and that's usually where the overload starts. Subtract the truck's drive (rear) axle when not loaded from the drive axle with the camper to determine that. My guess is that with 4407 payload, you're fine.
Also, the GVWR on your truck should be higher than 21,460. Most likely it is considerably higher, but it should be on your truck's sticker.