Can a performance document only have a manually entered overall rating and not section ratings?

Summary:

We would like to create a new performance document that has one section with three content items that employees will be reviewed on for the performance year. It appears that the ratings and weights can be disabled for the three content items and for the section, only allowing the employee and manager to make comments. We would like the manager then to have the ability to provide a manual overall rating (one to five stars rating) for the entire document in the overall rating section. Please let me know if this configuration is possible. Thanks so