This experience report charts a transformative journey in an introductory computer science course tailored for non-majors at a public R1 university. Central to the course are six immersive projects that are pivotal to student assessment. Transitioning to a mastery learning model, we championed an ambitious ethos for these projects: fixed learning outcomes with variable completion time — valuing proficiency over mere punctuality. Between Fall 2022 and Spring 2024 (4 terms in total), we explored a variety of project deadline and attendance policies. We observed that complete flexibility with minimal oversight adversely impacted assignment completion rates. Seeking to strike a balance between autonomy and structure, we happened upon a policy “sweet spot”. We found the best student performance came when we had moderate extension request “friction”, automated short extensions, high-touch longer extensions, proactive support, and required attendance. The primary insight is that mastery learning can yield outstanding outcomes — but the policies and support are paramount.