Lest ballhead novices overlook the significance of the drop slot location vs. adjustment knob position, if you do not spend money on an L-bracket for your camera, the drop slot needs to be at 9 o'clock to permit you to turn the camera CCW into Portrait orientation, or at 3 o'clock if you prefer to turn the camera CW into Portriait orientation. That causes the adjustment knob position to be less/more suitable for different folks!
I never knew there was a difference with Arca Swiss. With Markins and RRS, they don't offer this option afaik.


I will certainly contact you for any info.! 
