I used the following weights: 1 final exam point == 2 midterm exam points == 2.6 project points. Consequently, the projects were given a weight of about 55%. I set a curve first and applied the extra credit afterwards. A number of students were able to improve their letter grade in this way.
I ended up giving fewer A/A- than I would have liked. In addition to very good exam scores, I would expect A students to provide complete solutions for all 4 projects - including going the extra mile to implement eviction and persistence in projects 3 and 4.
To set the B/C cutoff, I looked for proof of individual performance in project 0 and the exams.
Click here for a histogram of final letter grades to see how the class did.
I would like to congratulate everyone who passed the class and hope you enjoy your holiday break!