I can provide a data point to 3:

Not at all! I have 2 days a week where I can't freely schedule my sleep and need to be awake for 8+ hours. This completely killed all attempts to implement any schedule listed on Polyphasic_sleep. To be fair, I almost made it with Biphasic but I tend to have a "long boot time" so I decided it isn't worth feeling like crap two times a day for half an hour.

In the end I invented my own schedule which, again, was only partial success. While experimenting on the schedules I noticed that I sometimes feel very refreshed in the "morning", but not often. I thought it's connected to the REM and tried sleeping multiplies of around 1h30m but either it wasn't connected to REM or my cycle deviates too much from the mean because experimentally I estimated this "good cycle" of mine to be 2h20m.

Then on a normal day I'd sleep one "wwa-sleep-cycle" two (for 19.4% sleep time) or three (29.2%) times a day which is not even close to Uberman on average, but I feel awesome. The interesting feature of this schedule of mine is that I can switch in/out of it immediately on the next day. Scaling to external constraints works well as a side effect of adaptation time e.g. before a tough day I'd sleep two cycles continuously or even get back to monophasic sleep with 3 cycles continuously.

Of course all this is original research on one specimen so may not apply to anyone else at all. Also, it took me months to do and now I only do it when on a tough deadline because one person would kill me if I'd set an alarm clock in the middle of the night, every night ;-)