Just being picky here, but what model Roto-Mix is this based on? A Roto-Mix 1220-20 has a capacity of 1220 Cubic Feet, or 34,550 liters (not 11,900 liters).
Every Roto-Mix I have see is 11,900, not sure why. Maybe the first people that did those based it off the base-game Kuhn mixer that was always 11,900. Thanks for considering the change.