You will be happy to know that coming in the fall we will have an observational form that you can use to score all parts of your project for all students.
Until then, would you be able to create a form and renumber each part - we can now renumber the questions. So 1-5 could be Part 1. Then renumber 6-10 as 1-5 again for Part 2 and so on. I would be happy to talk this through with you if you would like.
Let me know if I can help in any way,