I just looked up the drawing that Lister made of a Start-O-Matic CS1 installed in a masonary shed.
The cooling tank, also in the shed, is even bigger than a standard "200 litre" drum.
The diameter is similar at 23 inches, but the height is 47 inches, compared to normal drum at 34.5 inches.
It gives a capacity approaching 320 litres, about a third greater. That's about 70 imperial gallons, or 84 US gallons.
It seems to be the factory recommedation, but there are some puzzling aspects.
Like, isn't there such a thing as over-cooling?
And, where does the heat go, when it does eventually build up?
There's no fan, and it's inside an enclosed place, presumably (for silence).
Like the exhaust system, I'm baffled.
Jordan