A couple of thoughts comes to mind. First, lets double check to see if this curvature issue is on the rail and not the fuse/longerons. Perhaps if possible to trace the left side on a stiff paper/card board, cut it and flip it for the right side to see if how it matches. If it matches, perhaps if you can work on the C-01407 and C-01409 fluting to compensate for the difference? Also keep in mind that there will be a skin on that rail so as it is now in the video, the skin will stick out a bit.