Optimum phase margin Controller Design
When someone asks what amount of phase margin (PM) is acceptable, the answer should be &quot;what transient response do you want?&quot;. If you need a fast-recovery system and tolerate some overshoot or, on the contrary, you cannot suffer overshoot at all and want the most conservative design, then these are two different phase margin goals.
For a second-order system, without any zeroes, it is possible to link the open-loop phase margin (the one you measure with a network analyzer for instance) with the closed-loop quality factor (when the converter regulates). It is a simplified approach but explains well the link between the design goal and the closed-loop performance:

Practically speaking, if you can't tolerate overshoot and accept a sluggish response, you can shoot for a 90° PM. This is a very conservative design but military and space applications usually require this type of margin. For practical design, shooting for 60-70° PM is a good starting point, giving enough freedom to endure unavoidable components values changes during production and operating life. If you want a &quot;nervous&quot; system, you will purposely reduce the phase margin, giving a faster recovery time but to the expense of some overshoot. A value closer to 45-50° is probably a better fit in this case. Keep in my mind that this is a typical value and it will move up and down as explained before hence the necessary margin. You have to ensure through sensitivity analyses or Monte Carlo that the PM does not approach 30° or so or unacceptable ringing will occur. The ringing can either trip the converter over-voltage protection circuitry or damage the downstream applications.
Below is a picture excerpted from my APEC 2018 seminar illustrating how playing with the phase margin brings different transient responses:

That being said, some converters are easier to stabilize than others: the buck and its derived family (forward, half-bridge etc.) are phase-margin friendly most of the time. It goes differently with non-minimum-phase converters like the boost or the buck-boost to cite the basic switching cells. The presence of the right-half-plane zero can make the compensation strategy a difficult exercise and having 50° for PM is sometimes the best you can obtain. Finally, keep in mind that specifying numbers with 3 or 4 digits behind the comma - as you did in the question - does not really make sense when you go to the bench and solder components affected by large tolerance for some of them : )