I've also noticed that you're taking a 4 hour core sleep. It seems that sleeping in 90 minute chunks is recommended (ex. 1.5 hours, 3 hours or 4.5 hours). It is said that waking up between these 90 minute intervals will likely involve sleep inertia (desire to continue to sleep). I am still fuzzy for about half an hour after my core sleep, and I think it's mostly because of the time.Those of you whose gut reaction is, "Sleeping less to feel more alert? That's insane!" can pat yourselves on the back. Of course, it's possible that me trying this coincided with my body just deciding to not cooperate anymore, but for the last two early mornings I had to take a lot of extra sleep to not be completely wasted the rest of the day. That was not pleasant. So, I'm going to go back to four hours and see if I can pick up where I left off. (Trying 4.5 hours is also an option, but I'm trying to be methodical about this: if going back to 4 "fixes" things, then great, 3 hours really was the culprit for feeling like crap the last two mornings. If not then there must be another factor.)
One other thing that might be interesting about this experiment: napping during the day is different from normal naps, at least for me. I dream during these naps, for one thing (which polyphasic people say is a sign the body is adapting -- normally, you won't dream in the first 20 minutes of sleep), but the strange thing is for the first part of the dream I'm still aware of my real, non-dream body, and I'm not entirely assimilated into the dream -- I can think, "Oh, hey, I'm starting to dream. Must be mostly asleep now."
Lucid dreaming is another thing I've been curious about for a while, so I thought this was interesting. Not enough to actively pursue it, but interesting all the same.