Indeed, looks nice. Do a quick statics diagram on putting a sitting person on the overhang area, I bet there is a significant/damaging moment imparted to the roof, you may need to add some vertical supports?
Has already been tested. I already stood on the overhang and leaned outward to insert the carriage bolts. It flexes little and I weight in at 165lbs.
In normal cases a person would only lay flat on that section and even out weight. If you were really heavy and concerned, then maybe only have feet hanging off onto that section.
If you look at my image of the slide outs install, you'll see that they only come out 50%. 2ft under rack and 2ft out. Each slide out is made of 1" square tubing, unlikely to bend. Each slide out is attached to the bottom of the rack with 10 bolts to disperse weight evenly across the supporting cross members they are attached too.
The vertical supports on the roof will handle overhanging feet just fine or a light person laying on the overhang section.
In my case my kid will lay on the overhang section, my wife in the middle and my fat ******** on the driver side of my rig.
But you are right, I don't recommend standing on the overhang on purpose just to be cool and say it will hold out. Eventually it could lead to stress and the vertical mounts to the roof could cave the roof.