When i bought my siphon i taught a 1l would be a better choice since there will be times when i will need more than 0.5 l, obviously . My question is : if i add less than a litre, 500 ml for example, do i need to compensate the empty space with an extra nitrous charge ? Another question is : If my siphon is for cold applications only , what are the consequences of making hot foams ?