Just for future information, if you ever see an old bed rail laying around, grab it. They're harder and stiffer than standard, more malleable iron, and will do more to straighten your form with less physical weight. A local matress store may allow you to have a used set if their workers haul away the old ones after delivering new.
And if you slightly bevel the bottom edge of the form, you can flip the angle around so it lays along the bottom of the form instead of sticking out to the side.