Sorry. I copied the file from the backup and I forgot to copy the images :-)
Here are they

"And do you make some clean or trim before use images?"

Do you mean if I manipulate the images in order to get a better layout for work? In this case I have trim the front view, only for show the hull. The upper part I'll put when I finnish the hull (any century) :-P

"After a Rebuild, do you move theses "control points" for have a more fluent curve between other curves rebuilded?"

I think that in this moment must to appear the skill of the modeler, but always, when I've tried to make that, I ruined the result.:-)
But yes, I try to move the control points in order to avoid to make a taut surface

"What will be your strategy if thickness must necessary?
Shell? Sweep profil?..."

Shell...and...I cross my fingers! :-)
Sometimes, I have tried (if shell doesn't work) a offset, and then I have made the surface between them with Sweep + 2 rails (the borders of the surfaces). But I think that it is not the good way, and it is very tedious!

Sorry if I can't help more. I think I'm not a good example.
Maybe if Mark Brown read us, he'll give us a good tips for get good results! ;-)

p.s. I'll go away for 3 days...read us then!