Its a bit early for me to know for sure but I do
expect if built with care 900kg would be achievable.
I expect my floats beamed and painted will be well under 100kg each and that leaves over 700kg for main hull rig and sailing gear.

I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!