Convection trumps conduction. The ground is retaining some warmth that is gone once you're suspended. The slightest breeze passing by you will suck the warmth from you in a blink. Not sure, but it sounds right. I have slept on the ground only a few times and those were decades ago.
I assume you're connected to the front roll bar by the windshield and the opposite rear corner. What is that distance in an LJ? And what is the length of your hammock. Does your hammock have a ridgeline?
I have a friend who hangs at BIG negative temps.. like -30F to -40F. Those temps can kill you. Not for me. Things wrong REALLY fast at that temperature. Anyway, he turns his coat inside out after zippering it up with the arms inside and slides his feet in, right over the quilt. Not over the hammock. That might work but I suspect you don't own a mummy bag big enough to encase the entire hammock, especially if there is a ridge line on the hammock.
So one of the very early Hennessy hammocks was a bottom entry setup. I never tried it. There are tales of guys dangling their participles out the bottom entry to take care of business. Just keep your shoes out of the way. Far more common is a pee bottle. A large dedicated Nalgene. Kills two birds. You pee in it, so that problem is solved. Then you toss the warm bottle in the foot box of your top quilt to warm your feet. I never did that either. I can make it through most nights without needed a biology break, and if I do get up, no problem getting back to sleep. In really cold weather I have boiled water, poured it in a Nalgene put the Nalgene in a cozy, then in a ziplock and tossed that in the foot box. It doesn't give off enough warmth to risk it leaking. A wet quilt is game over. Truth told, just throwing the cozy covered Nalgene in the bottom of back pack (usually hanging on the foot end tree) is enough to keep the water from freezing. PSA-Not all Nalgene's can handle boiling water without deforming and make sure there is no air in the Nalgene after filling it or it will compress while it cools and you're have a hell of a time unscrewing it in the morning. Ask me why I know these tidbits...
I suppose this makes sense.
I am wrong person to offer any feedback on the whole fluid, alcohol intake & peeing..
I have a tradition that is upheld every time I am on the trail. I usually drink it all on the first night so I don't have to carry it.
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