Simon.
3 bar luboil supply servo.
I am happy you found the supply pipe going on the outboard side of the engine. Your suggested revised systemsketch is of course according to you find. I have below indicated how I guess the details of the servo might be. After the branch off to the Roots blower bearings, I guess they enter on both sides, the supply pipe enter the servo as shown on the drawing. The two drainpipes runs from the servo separately ( not to have any pressure interference) and join further the maindrain from the blower before entering the systemtank valvechest and into the tank.The oil from the servo is not contaminated so I don`t believe it enters the dirty oil tank.
Tore