I don't see why not. The roof racks are real and can carry a load. Shouldn't be a problem unless you don't have the women or dog.
I'm not saying your math is wrong, but I want to point out one thing that the picture... hides.I don't think the roof rack is designed for lateral stress. I wouldn't count on that. Those two in the hammock that long with that much sag are exerting a lateral tension exceeding 400 lbf if my math is correct.
I wouldn't do that as from your description, you would be pulling down on the spoiler, which I suspect would result in much badness.I'm not saying your math is wrong, but I want to point out one thing that the picture... hides.
The force is not perpendicular to the center of the roof rail (farthest from the connections to the roof). If you'll notice, it is pulling toward the back of the rail where it is fastened to the roof.
Again, I'm not an engineer, and I'm not saying this makes everything okay, just pointing out that you have to consider the perspective of this photo, where the force is applied in relation to connections, and for how long...
If I WERE (not saying I am) going to do this, I'd tie a rope between the roof racks, at the back where they connect to the roof. Then I would tie the hammock to the center of the rope crossbar I just made, so that the load was distributed between the racks, at the fasteners to the roof. I suspect I'd sleep well enough by myself in this configuration. The person I'd share with only weighs 120...in a soaking wet fur coat... so I doubt the forces would be an issue. But that's just my opinion, YMMV.
Make the "crossbar" long enough to loop under the spoiler.I wouldn't do that as from your description, you would be pulling down on the spoiler, which I suspect would result in much badness.
Looks like under the roof to the roll bar on the wrangler. Perhaps the other one has a roll cage installed, or they might have it hooked up to a seatbelt anchor point or something else strongly attached to the unibody.thanks all,
do you have an idea, where did they tie rope