If it was a short stop, we would sleep right there in our positions.
TC, Loader, Gunner and Driver.
The Driver on a M1 has the best position, a 2/3 laying position.
Long sleeps, we would sleep on the back deck, if raining and depending on the situation, we would turn the gun over the back deck and erect a tarp. The M1 puts out alot of heat and the back deck was very warm.
In the First Gulf War, Many a times our Driver would fall asleep on the move. The steering had a "T- Bar", and similar to motocycle grips for giving gas. The drivers fastened a piece of rope from the T Bar to under his legs to keep the Tank in a straight line, and full gas.
Thus having nothing to do, would fall asleep.
We never slept on the ground.