Any chance you could add an option for 400kHz ws2811 strip for your octows2811 port? I imagine it would be an easy addition, I accidentally ended up with a grip of 400kHz strip and it’s not playing nice 
Issues on github is a much better way to track feature requests/bug reports 
That said, pull the FastLED3.1 branch - there’s now definitions for WS2811_400 for the various ports (e.g. WS2811_400_PORTD).
Note that this will only work with the various PORT* parallel versions. Modifying the code to use OctoWS2811 in 400Khz mode is a bit trickier, and I may not get to that tonight.
Seriously though, dude, why haven’t you moved everything over to APA102 already? 
(Have I mentioned I can’t wait until Sean moves over?)
Also, on the off chance that you’ve pulled in the last 5 minutes, pull again - added OCTOWS2811_400 to trigger using the 400Khz version of the OctoWS2811 controller. Hopefully, not in any position to test any of this so - you’ll be the first to run it at 400Khz!
(I’ve been using these at 800Khz on a bunch of projects so far this year)
Thanks! that did it!
( I submitted a slight typeo issue to the github)