has anyone made their own tonneau cover? i want to make one that fits up to my tool box and the retail ones are way to expensive for me. im thinking about making a frame out of 2x4s then either lay a piece of fabric on it or a sheet of plywood. then i could possibly use a c clamp to attach it to the bed. im still thinking about what to use to attach it to the bed. i want it to be easily removable.