The three objectives

Polyphasic sleep has three goals you can aim for:

• Health
• Reduction
• Flexibility

Unfortunately, you can only really maximize two of these, or strike some balance between each. Health is the most important usually, so it should get a significant amount of attention. That means ultra-reducing schedules, or strongly reducing and also flexible schedules are out of the question. And so is random sleep, the ultimate of flexibility, leaving no space for health.

• For MAXIMUM health: Choose non-reducing schedules only. Reducing ones aren't unhealthy per-se, but to maximize health, non-reducing is best.
• For healthy reduction: Choose something above 5h of TST. Anything below that is going to be somewhat unhealthy, or so inflexible that you need to be at home 100% of the time, with zero surprises, for them to work.
• For healthy flexibility: Choose something with a 4.5h core at the very least. Something like M3Ext is quite good for flexibility once adapted, but consistency is key during adaptation still. MX on the other hand is near-non-reducing but flexible from the start!

Once you have chosen a schedule, read how-to-adapt!