I just finished the first bases of Principes, with a base of Triarii lurking in the background.
I am very pleased with the decision to go for 3 ranks on a 60x30mm base even if it means painting 1/3 more than I originally planned for.
Each legion will consist of two units of Principes, two of Hastati and one of Triarii, each unit will consist of two bases. Making each “Legion” 10 bases strong. In addition each legion will have two units of Velites based on 4 30x30mm bases so they can be in both open and closed order as needed.