Sebastian
Very interesting, thank you.
That looks like a Thornycroft boat but it is not.
Between 1878 and 1881 Italy bought five torpedo boats. Nibbio and Aquila from Thornycroft and Avvoltoio, Spaviero and Falco from Yarrow.
Clio (1882) was the first Italian designed and built torpedo boat but seems to have been very similar to Nibbio (See message from Wujek Andrzej - Sro Kwi 14 2004, 9:18 )
If you want detailed plans of Nibbio it is possible that the National Maritime Museum at Greenwich, London may be able to help.
On Warship.com I saw
AChoong@nmm.ac.uk suggested as a contact in the museum's Photographs & ship plans section.
If you can make do with less information I suggest using the plan of the New Zealand boat found by Jim and the sections in Rob's plan of Torpedo boat No. 80. The hulls of all the early torpedo boats were very similar.
Cheers
Maurice