oh ok that should work... I could see a problem though, if the 2x4 is slightly warped (as they often are). The advantage of using angle bar to cope a large box is that your skis can accommodate any warp-age because the surface is so wide. When the surface is narrow, the skis might naturally tend to slide off to one side or the other. Imagine if a flat-bar twisted as you slid down it... it would be almost impossible to slide. Just make sure your piece is completely free of any torsion. Also, make sure you support the 2x4 properly, because if it bends with your weight, it may end up bending the angle bar as well - leading to a permanently bent rail.