Screen assembly for a vibrating separator, the screen assembly including a frame having a pair of parallel opposed sides and a pair of parallel opposed ends, a convex underside of the frame, a reverse-crowned top side of the frame opposed to the convex underside, and at least one screen cloth layer fixed to the top side of the frame for separating solid materials from liquids, where the deck of the vibrating shaker has a profile which is substantially planar or crowned.