In another item in this Tip Bank (see link below), we mention that you can co-locate secondary instances within the context of the caller. If you don't need any services at all for your secondary components, then you don't have to configure them as COM+ components either. You lose the deployment and administrative support that you get from COM+, but you get improved speed and less memory consumption. Prior to COM+ 1.5, this also takes away the configuration trap for "Must be activated in the callers context".
In COM+ 1.5, you can get a similar effect, but without giving up the deployment and administrative support by saying "Must be activated in the default context".