I can say I free feed Juni (and my cats before), but I never give them too much. If she still has something, I wait until she finishes everything, then I give her more. I am not worried she will starve, she always ask if she wants more. When I used to feed her with dry food (I think you all know, I switched to natural food - for me and her), she never ate the amount that was written on the package, I never worried. As I said, if she's hungry, she KNOWS how to ask, yes she does!
Our feeding system for Nipo is similar to Vio&Juni's. She gets free fed in the sense that she asks for food when her bowl is empty and she is hungry. Sometimes she asks for food when there are a few "dingles" (my Dad's word) left in the bowl, and in this case she has to eat those before we give her more. This system works well except sometimes we get ant problems. Nipo isn't overweight, she's the perfect size or if anything a teeny bit chubby.