A lot of flavour!
With a 1 egg pop-up mix I add the same amount of flavour as recommended for 6 egg mix. So in your case use 5ml.
When you work with a flavour you get 'nose blind', basically your sense of smell is overpowered and you no longer notice the smell. Exactly as your work or home, they have a smell that you don't notice, but others coming in do. (There is nothing like wet stinking dog smell, you only notice that for a while)
To keep shape, roll them with a mix as dry as you can comfortably work, almost too dry.
However if you are making the pop-up mix from scratch, then some ingredients do take on water and mishape them. I often have mishapes (which I am happy with myself) when I roll them. Don't boil too many at a time, keep them moving in the pan, as one side always sticks up out of the water.