Sam, there can be no downside to getting the larger capacity - assuming the unit will fit okay!
That’s the advantage of the gas system over the foam - it doesn’t leave a horrible mess if triggered!
Rob, the 2.0Kg cylinder is 2cm longer and less than 1kg heavier. Cost around the same so may as well…?
Agreed, go for it - the more chance of stopping a disaster, the better!
Is that Ying’s handbag you have taped to the dash Rob?
Nah Tim - my spare underpants!
PS Do you like the shiny knob? 
Did you nick it off a Tuk Tuk?
No, a dik dik 
Reading “foam extinguisher” i always have to think of the one time my friends dad pushed the “test” button in our rallye car and triggeres the extinguisher. What a mess that was.