I haven't really had anything to add about my experiment in a while. I tried to keep a consistent schedule for over 30 days, at which point it became clear that I'm not able to do that every day. I think it's really necessary in order to make a plan with a short core sleep work.
Days where I had no choice but to give up my morning nap or where I didn't get high quality sleep during it were hard, and after several days of that in a row, I decided to give up on forcing any schedule and just sleep as my body felt like for a while, with the caveats that I take a nap every day (whenever I could work it in or felt like it, no certain time) and that I keep an early wake-up time to stay in the habit of getting up and staying up when I first awaken. There are many benefits to getting up early, which I won't outline in detail today. I settled on 5 am; I think this is a commonly picked time for a reason. It's early and has you waking before dark, but not several hours before daylight. It's easy to maintain without extra effort.
I've been staying busy and haven't given much thought to sleep schedules lately, but I want to take some time to see how much sleep I seem to "naturally" want after a few weeks of adjusting to this program of the daily nap and waking up at a set time each morning. With that information, I'll decide what I'd like to do in the future. Right now, I seem to be sleeping about 4-6 hours at night, plus a nap of 30-90 minutes.
I still think that napping at least once during the day adds a lot of benefits, and sleeping shorter hours at night makes one more likely to take the nap and get the most from it. However, with not being able to get a nap at a consistent time, 3 hours is too little for the core sleep. I think I need at least 4.5 hours in order to not get fatigued if I miss my nap.
Anyway, the summation of my 30 day experiment: the 3 hour core plus 90 minute nap is adequate, if you unfailingly take it everyday at around the same time. However, expecting to be able to do that seems to be unrealistic. I don't know if I would continue attempting it in the future, even if I could fully set my own schedule, because it is too hard on you if some unforeseen event causes a significant deviation. I'll have to do some more thinking about whether I'd like to attempt any other schedules. Right now, I'm not feeling that "gaining" a lot of hours by sleeping less is worth it if I risk fatigue.
Although I haven't gotten the least bit sick since starting this experiment, I've had some days when I felt bad, and I questioned whether having that kind of stress on a regular basis is healthy. When dependent on regularly scheduled naps, getting really worn out is a daily possibility. Even if I got all of my sleep, just spending all the extra time working seemed to leave me more tired.
I think more recovery time is necessary, although I still think that taking all your sleep in one 9-hour go is not ideal either, so I am not advocating giving up polyphasic sleep. I just think some other scheme than what I was doing would be better for those who don't have a regular daily schedule.
Anyway, I'm just doing whatever comes naturally to me (with those two restrictions) for a while, giving that a try, and considering whether I like that or if I want to attempt something else. Experimenting has been fun, but I don't think it's realistic for something long-term at this time. My main goal is to add to my health by taking more naps, and not to cause myself fatigue by doing something that results in missed sleep. I'll evaluate what works for that, and plan a new course.