I've been doing a 20-hour 3 day work week (50% of total pay) for a few years now and I love it. I'm outperforming a full-time colleague in total output. Edited to add that the 3 day work week totals 20 hours.
What does your full time coworker say about that? Are you concerned at backlash or retaliation?
No backlash or retaliation so far after more than 2 years.