I think most make their shelters too large and "roomy." I've seen a few that you could sit up in. This isn't a tent. You need them snug so they hold in your body's heat. When you make the frame, make it so small it's difficult to get into, and then lay on the debris, like boughs and leaves - at least 3 feet thick, preferably more. Don't forget a thick layer of debris inside the shelter to lay on and insulate you from the cold ground.