With the current methods, It will be 3 parts. The wing with the turned down ends, and 2 supprts. I will look into non-CF parts but i plan to have this so low to the trunk lid, i'm not sure exactly how well it will go. It would pretty much be the bracket on the trunk right up against the bracket on the wing. I'll mess around with it after the wing is done and figure out the best way.
I also plans on only having the wing about a centimeter thick so i don't really know how much use I will have for internal ribbing.
The base spoiler is the OEM spoiler from a Nissan Silvia S15. The center support and taillight from the S15 have previously been removed and will no be present in my spoiler. If can't find any specific measurements you would like, I'll take them tonight and post back.
Edit: as far as actually making the parts, I'm thinking about using infusion to actually make the parts. It seems like if i take my time during setup and do it right, it will be hard to screw up the part.