I tow my 2011 3300QS with a a stock 2005 F250 CC 2WD SB 6.0L. When configured for a long trip, my computations indicate that I start limited by the max gross for the truck. I've weighed the truck and have computed axle weights and center of gravity. All other weights are within limits with the bottom line being I am at 86 of the CVWR limit. Loading aft helps on paper, but load it with the CG too far after and you lower the pin weight, which makes the chucking more pronounced. I've towed empty and I've towed heavy, overall performance and handling are not materially different regardless of weight with the exception of chucking. The truck squats about 3 inches or so regardless of pin weight.
I wish it would drive like BWN 740iL, but it doesn't. You start slow and stop longer. It has the turning radius of a US man of war. I wouldn't recommend attempting to parallel park. I wish it got better mileage. I experience around 11-12 MPG driving around 65 or so dependent upon terrain, weather, traffic, and road conditions.
80% loading is great, but your not towing a big 5er with a conventional pick-up truck. My truck on the scale empty is at 72% of the GVWR. If you want to tow a big 5er, expect to be near some limit or another.
This rig is a lot heavier then our old TT, but weight's only one factor. I appreciate all the safety arguments, but for anyone who has flown or operated complex machines at the published limits, you know that operator technique and judgement are the critical factor in the safety equation.
It's equally important to point out that weight limits are not driven by safety alone. In reality component life objectives have a much stronger influence on the limits than safety. The more weight the more you demand from the equipment the more likely you are to experience a materiel failure. This is the root of the tire is the weakest link thread.
Bon chance,
Mouse