That 5000 lbs tow rating, does not allow any weight for aftermarket accessories, passengers, and cargo. As you add those things, your tow capacity and available payload are going down, pound for pound.
Check your drivers door post. Look for a tire / loading sticker. It will give you a number for max occupant / cargo weight. Take that number and subtract weight for all the people and stuff you would normally carry in the vehicle.
Whatever is left, divide that number by .13. That will give you a ball park number for trailer weight that will put you close to max.
Example:
Say the loading sticker says 1000 lbs, you have 600 lbs of people and stuff. Divide 400 by .13 to get a 3076 lbs loaded trailer weight.
Keyword in the example is "loaded" trailer weight. That means, when the trailer is ready to go camping, it weighs no more than your estimated loaded weight.
