Just to keep track of the current questions that have most interestingly emerged as I do this....any ideas welcome, experience from others welcome!
1. To what extent does it matter if the timing of the 90 minute nap varies? (Of course when "stuff happens", it will vary, but I wonder whether it will be best to just get that nap in sometime, like one brushes one's teeth (every morning, every night at least, the actual time matters little to me anyway

), or whether it is better from a sleep standpoint specifically to have that as regular as possible. May well be a highly individualized matter. I'll post my findings and hope others might do the same.
2. When there is an interruption (with holidays coming up, a real apropos time to be looking at this), is it best to just get right back on a previous schedule? I'm thinking yes, and that's what you were saying, David. Especially so for biphasic sleep, I would think compared to polyphasic.