This is my favorite survival shelter. Each of my boys have one int their PSK/CamelBack. I put a strip of duct tape with a metal washer on the bottom of the bag and three on the open end. I stake the closed end and the two open end tabs. The one tab on top has a taught line knot pre-tied. If a tree or bush is handy I can tie it open with the end of the cord. If not I can push two sticks through the tight line knot and have crossed sticks to hold the bag open.
The bag is large enough to sleep in stretched out. It will protect you from the wet ground and the wind. It will protect from rain better than a tube tent. You can tape a $0.99 poncho to the opening to protect from rain if needed.
Give it a try!
Add a couple trash bags to fill with leaves or pine needles and you have a nice blanket to keep you warm. Use clear trash bags and you can use them for transpiration to get some water from trees.