For the SP2, the service manual asks for 498 +/- 2.5 cc of fork oil.
For SP1 forks, it asks for 513 +/- 2.5 cc of oil.
Now what that equates to in oil level I'm not sure.
However, I've bought the Traxxion Dynamics fork cartridge kit and they recommend 120mm of oil level if that is any help.
Just in case you didn't know, the oil level only affects the air spring effect towards the end of fork travel. You adjust the oil level to prevent the forks from bottoming out at full compression.
The air spring acts as a safety cushion. Otherwise it has no overall effect on damping.