Thanks guys! I've just received the mount

I am just going to install it and under Preperation it says
2.5 Slide out the brass back focus locking pin from camera and store in included box (which box :O

)
2.6 Re-install back focus screw with Allen Key until flush with bottom of camera.
So I am confused, am I doing exactly as this says? If so why? In my mind, I need to remove the C-Mount to get this bad boy working.
Off topic, how do I know which thicken shim I would like to use? I guess its lens dependant and I should look at the lens I am using for it? (answered: Ah, its on the reverse of the sheet under "6. Back Focus Adjustment)
Also it would be great to know why we removed the fan screw

But otherwise what an absolutely fantastic mount this is

I am pleased to see c-mount go away a little bit