Code:
FFMpegSource2("VIDEO0007.mp4",atrack=-1)
AddBorders(160,0,160,0) # 160+480+160 = 800
Trim(0,729) ++ Trim(730,1543).TurnLeft()
160 because you need to add a total of 320 to pad the clip to square proportions, as already explained in the earlier posts.
Resulting video here
www.sendspace.com/file/6n6yrp