haydie, thanks for replying.
I see your point about adding them as separate products. It would solve the specification issue, but if I were to add other products (e.g. Clif Luna Bars and Builder Bars), I'd soon have a product explosion with several hundred products and no variants.
What I was trying to say was that it seems to me like the store's product model should allow for variants to override/add to the product specification on a general basis. That way, the product model can adapt to the real world rather than force-fitting the real world into the product model.
Also, doesn't it make sense to have the ability to add specification attributes to the SKU (i.e. the product variant)? Isn't that were the specification logically belongs? A lot of the specification would be common, of course, which is why I'm still in favour of adding spec attr to the product, but some would be overridden by the variants.