Hi Leo.
Nice to find you also here :-)

In Italy, the North American Cedar is a very valuable wood, very difficult
to find and much more expensive than Okoumè (solid).
......
Alternative could be Spruce, light as cedar but less durable than
okoumè.

I have read somewere that in NZ also Paulonia (or Paulownia) as been used.
Paulonia is known in Italy mainly for flowers, but it is a fast growing
tree, is really light (lighter that the best WRC) and is claimed to be
extremely durable in salt water.
It originates from Japan or China... I don't remember... but I know that it
exist one organization for paulonia wood promotion also in Italy....
You can try a googgle search....

Paolo Zini