@Kasper_Kamperman Re: your comment on Gitter about the current draw for APA102©s calculated by LEDstimator; it was either a datasheet I found, or going off FastLED’s empirically-derived figures. I remember it being all over the map though—if you can find two different datasheets which give the same numbers for the same chip, I’ll be amazed.
(Ok, doing the research again… This datasheet: http://www.adafruit.com/datasheets/APA102.pdf says “0.2W” @ 5V, which means 0.04A; but then this one https://app.box.com/s/8oevda04rtxruji01vje says “source current tpy 20mA”, which I can only presume is per colour. Then this (not pretending to be a datasheet but anyway) https://m.flickr.com/#/photos/111277734@N07/14117653018/ says "10.8W/m, 36 pixels/m which would add up to 0.3W pixel, which @5V would be 0.06A)
So who the hell knows?! I guess I need to get 5m of each of the types I can get my hands on, a sensitive current meter, and do the experiment myself.