I am using vue-loader (http://vuejs.github.io/vue-loader/start/spec.html) to construct my *.vue single-file components, but I am having trouble with the process
The proper way to do this would be to use mixins: http://vuejs.org/guide/mixins.html
Think of mixins as abstract components, which you can extend. So you could create a mixin with any functionality you wanted to have in both, and then just apply it to each of your components.