In a hammock, the center of gravity slides towards the lowest spot. In a man, the center of gravity is in our chest. Therefore, it's natural for our chest to gravitate towards the lowest point in the hammock...which ends up crowding our feet into the foot end of the hammock and leaving a huge space over our heads. But hanging the foot end higher means the hammock's lowest point is closer to the head end rather than in the middle...so when you settle your body is actually more centered in the hammock.
Well it doesn't sound so unconventional when you put it in scientific terms like that.