Hi Simba, this is video where I made Acva riva and you can see how I made hull: http://youtu.be/WaCFQOaTjTQ
Also this is thread where you can see model and other stuff: http://moi3d.com/forum/index.php?webtag=MOI&msg=6236.1

Hi Simba
I have had a look at your drawing and found most of your curves have 5 points but some more.
Also the blend line produced by these curves along the length of the hull was a little wavy.
I have rebuilt your cross sections using the straight lines and blending them and then did a loose loft.
I also came across this video that may help
http://www.youtube.com/watch?v=hgjxO5yuRxg&list=PLNR63yhSxBmTXrOFDRnorMkDj_lKf1_3L
If I remember right you posted a similar problem with a catamaran hull so I attempted
to do it based on the Youtube video which I have added to the attached drawing.
Hope this is of some use.
Barry