I think I should rename this "The Oversleep Chronicles", because yes, I overslept again. Set my alarm for 10:30am, got up at 1pm. This time I have no excuse. The alarm went off. I walked over to it, turned it off, and went back to sleep. The room outside my bed just felt so cold, and my bed felt so warm and cozy, and my mind was so groggy.
I just didn't have the determination to stick with it despite the inevitable discomfort. But now I do. There'll be no oversleeping next nap. I also think I'm going to try napping in my clothes, as some other polyphasics have recommended, so there'll be less disincentive to get out of bed.