There certainly are many ways to make a six meter cat and an eight meter mast fit within the four meter limit. In my opinion the big problem will be the time and work it will take to assemble and disassemble the contraption.

The Tornado is definitely not the boat for this. It is too complex, its floats lack enough flotation to carry camping gear and it is built for speed, not to take the abuse of daily journeys and night camping.

The closest match to your needs are the Supercats / ARCs. They were designed and engineered to be fast, simple, efficient and easy to assemble/disassemble. A Supercat / ARC 19, 20, 21 or 22 halved in the right place, properly engineered for re-assembly of the floats and rigged with a two part mast would probably be your best bet.

If you find a used one close to home, contact the factory (Aquarius Sail) and discuss how to cut the floats and mast to fit within the four meter limit while still keeping (or improving) the safety factors.

If there are no used Supercats / ARCs in Italy, you don't need to build the entire boat. Find a suitable cat with high flotation floats, simple and easy to assemble / disassemble. When you find it, sail the boat, learn all you can about it and then discuss the best way to cut the floats and mast here, or in other fora, like the Multihull Builders Yahoo group, for example.

Good luck,
Luiz