Thanks for taking the time to do the drawing, the closing plate idea was going to be my strengthening measure if the channel flexed to much. Using box section as a rail but rotated had occured to me, but I was put off by the radious on the corner of steel box section, Ally has a nice square corner but wouldnt last long with the bearing running on it, I'll try running a bearing along the edge of some steel box and see how the V matches the radius.