I think the official is the following each day:
1 spoon of mix a mousse
1 bar
1 teaspoon of flavour
so if you don't have a bar or a flavour then I guess you could have more mix a mousse. but I don't worry about this, if I need a mousse then I have one, and I have as much flavouring as I need to get the water down and it hasn't done me any harm. as I see it, better to have the tiny extra carbs from these then go for something off CD!
hth