restructuring tables and model relationships in order to use STI

Hey James! I'm going back to the garage app and want to implement some of the things I learned from you over the last couple of weeks. As a first step, I'm restructuring the models and databases. Planning to use STI for Users (with Customers and Employees inheriting from User) and for Repairs, with Invoices and Estimates inheriting from Repairs.
Actually, doing this without losing data will require some sql. Let's just do this by creating new migrations only, deleting and recreating the columns in their new homes. Next time I see you we'll cover some sql, probably enough to get this job done :)