All right, thanks for all this inputs.

@Pilou
>>Helpers are your friends :)

Sure, when you know how to correctly use them :)


Thanks Brian for you video, I get it now !

@Michael.

Well thanks again to taking some of your time. S will be my new shortcut for this temp snapping script !

>> One thing that can work for some simple symmetry is to drag out your construction lines before you start placing any points.

Yes, I understand the method, however I have some problem to visualize (is that correct) where to place the guide (and the control points) before drawing the curve.
But now that I can snap the guide after the control point creation, it's perfect for me !!

Merci :)