I am amazed at how well the APA102's tolerate low voltages.  As an experiment

I am amazed at how well the APA102’s tolerate low voltages. As an experiment I set six meters of 144/m all to full white, and connected them in series with only a 3A 5V power supply at one end. By the other end of the strip the voltage was 1.8V and the color of the LEDs was totally red at that end, yet there was no flickering. This is encouraging, making me think that I will be able to get away with putting 5V 3A DC/DC’s between each strip and definitely not have to worry about power-induced flicker, even if I won’t be able to get full white power.

BTW all LEDs at 0x777777 seems to be about the whitest white that I can display with 5V 3A feeding one strip of 144/m so I think I’ll be okay with that supply for normal things where full white is used sparingly.

Mind sharing the exact strip you were using? I’ve got some APA102s here and my experience has been the exact opposite. Once they get below about 4.7 volts they start glitching pretty bad. I can take WS2812Bs down to 3 volts and the blue and green emitters drop out but the data’s still OK.