Maybe if you have little girly arms...I can hit the back curtain on a ball that clears the net by 2 feet if I swing with an Eastern grip completely flat.
LeeD has a point. you have to be discerning about which ball you can hit flat. A ball at shoulder or chest level can be hit very flat with a little bit of topspin from followthrough (which is inevitable) that is aimed at about 2ft over the net will most likely go in. Waist level shot not so much.
on a second thought, 2ft might be a little high. say about a foot.