This object 3dm (clic on the link) http://moi3d.com/forum/get_attachment.php?webtag=MOI_FRANCAIS&hash=9ad1777e162cb0804a31246c5fa6aed6


must have its "side faces" like the side orange form (the internal forms must not move) the orange form is not a rectangle
What is your process for obtain a result form without lines on it (construction or intersection)
In this little video I have made only the right part (form is not symmetric)
http://www.divshare.com/download/944385-5cb (sorry the interface of moi is in french but you will understand the images :)
but maybe exist a more speedy trick?