Greg,
I wanted to set some expectations before I fix this bug. Currently, DevForce doesn't fully support design time data. In particular you can't use code-first at design time. There are security constraints at design time that cause DF to fail when trying to load the metadata. You can suggest a feature on our new User Voice site for DevForce if full design time data support is important to you. I can fix the current bug in Cocktail, but that only gets you so far.