How much weight is too much?

Assuming 1000 lbs additional weight, an additional 3HP will be required at 60 mph. Oh dear!
If you added height to rig, ea additional 3 sqft of frontal area is equal to HP of 1000 lbs, or 3HP. Add a foot, 1000 lbs, equal HP needs of 4000 lbs.
BUT!!!!!
If said trailer is more aerodynamic!, you may need less HP than you do now, and get better performance and mpg by .1!
Also remember, tow ratings are a performance/warranty rating. A 2011 is out of warranty. Performance wise, every one of us has different assets, so expectations are different.
Reality, assuming a 2500 series, no big, a 1500, might be a chassis retrain issue.
OPs call. I'd do it in a chebby heartbeat if an 8 lug truck!

Marty

I'm conservative on my weights, I like to have a cushion of extra capacity, and not work the vehicle as hard.
Assuming it is a 2500, I don't think it is a safety issue, but just working the engine and tranny really hard, and possibly wearing them out quicker.

OP also doesn't give numbers for weight over axles and tires. Wanna bet it's overloaded?

My last F150, a 2007 with 5.4L CC, LB with 3:73's I routinely had the rear axle overloaded by 300lbs with trailer in my sig that weighs in at 7000lbs on the axles and over 900lbs of tongue weight. Very sad that that overloaded my truck.

The OP asks how much can he pull ..not how much load can the truck carry. Big difference.
The '11 2500 chassis sure won't have any issue carrying 3000-3200 lbs in the bed however 11900 lb trailer is a lot of weight for a smallblock.

I pull a 11200 lb 5er with my 2500 Dodge/Cummins/NV5600 6 speed manual with 325k miles on the odo.

I made a living pulling heavy GN trailers (25k-32k gcw) for several years with the old 454/460 big blocks massaged by Crietz automotive (tow motors) to around 300-325hp and 450-475 torque. For my use I wouldn't be comfortable towing that much weight with a smallblock.

I would guess if the truck was designed for 150k miles at max loads it would make it 145k miles before 1st over haul.
You also will need a good Maintenance schedule operating at those weights.

Man you really opened the door. Sit back and be ready to be beaten for even thinking about doing that.

“I feel like the tow guides are a little conservitive and you can probably get away with pulling a somewhat heavier trailer than the truck is rated for.”

I wouldn't put my family or OTHERS in danger based how you “feel” and can “get away with.”

At this point, you are looking at dangerous ground. Generally they give you the maximum towing capacity with one operator in the vehicle, so that the weight of your truck loaded, and the maximum weight of the trailer will not exceed the Gross Combined Vehicle Weight.

Now the catch, how much weight are you actually carrying in the truck, and yes that includes the passengers, the weight of the hitch, the stuff in the pick up box too.

Then are you implying that you will only load a trailer to 400 pounds of goods?

Then the trailer weight is often the bare bones trailer, and doesn't include some things that are optional extras for the build like the A/C, extra battery, TV and others.

So you see, adding 1000 in the truck takes away from what's out back. It will pull fine, but will it stop? Will it respond correctly in an emergency?

As you know, your truck will not instantly self-destruct as soon as you exceed you truck's rated capacity. Having towed coast to coast at or over capacity, you know exactly how it does. Adding an additional 600 lbs will not make an appreciable difference, except in the head of someone who is obsessed with the numbers.