Yes, it is with 255 buffer, photo mode. Every time you switch yor cam on you have to set high iso noise reduction to multi because its always gets back to "single" setting. I don,t use hack mode, I have to see what I am recording. Other settings its force left. Remember, that every first time shooting (after switching on) is shorter, second time its getting full lenght. On sandisk 45 64GB I have 38-39,5 write speed.
Hacked mode is when you press Q on raw options there is canon, auto, hacked, something. Hacked mode freezes LV screen on the first frame so I beleieve It would be good only for static shots because you cannot frame properly. Sometimes its improving write speed and sometimes not, seems it depends on the resolution.