From operating several Raven IIs for thousands of hours and monitoring oil closely, we determined that keeping the oil at (but not above) 7 is the way. The amount of oil lost below 7 is a lot less than if you try to maintain 8.
The Lycoming handbook says you can use as little as 4 - but that would be foolish in a helicopter.
You can always spot the overfilled Raven II in the hangar - small pool of oi which drops off the breather pipe. Tail area covered in a film.