Glass vs. build up
Octane,
I dont believe anyone can give you any real info on possible weight savings because no one has any idea about your skills.
If you build it up it can get real heavy unless you can keep the former count low and minimize the use of ply except in the high stress areas. You have to be smart about where the wood is going. Example; a top quality aircraft grade 5-ply 1/8 thick is usually stronger and lighter than a cheap grade 3-ply 1/4 thick that is commonly found on the LHS rack.
As for laying one up I have to agree with Russ's comments. But if your really good you may be able to save 4-8 oz by using fiber-glass. From what I have experienced, generally the larger the model the greater the possibilty to save weight by using composites.
Since you plan on building more than one, why not build one up and lay up another. For the glass fuse you might consider the lost-mold-method aka investment casting. Make a mold from foam and lay the glass over that. Then cut and melt the foam out.
Cheers.
James