I believe you can have yogurt in later stages of "ladder" once you are adding in carbs - however it is not true that there is a "magical" formula in yogurt - you do need to count all the carbs!
There are some other websites which have info on making your own yogurt - some have made it out of half and half to lower the carbs.
I have found a full fat plain yogurt which is 8 carbs per cup and will occasionally have 1/2 cup w/some splenda or sf syrup...very rich, creamy and filling!
Froufy