Hi Willw,
The oil line enters the top weir dipstick hole and stops just at the upper oil level, by adjusting the stop collar on the pipe I can set the depth that the pipe reaches to. The oil tank is sealed and only allows oil out when air can enter the pipe from below, ie as the oil level falls... As a bubble of air enters the tank, it lets a few drops of oil out, the oil level rises, and no more air enters the pipe, oil stops flowing out the tank....
The height of the tank itself has no bearing on the oil level in the sump whatsoever... But the depth that the pipe reaches into the sump does!
Cheers
Ed