What is the maximum amount of skin that can be removed during a lip lift without complications?

Thanks for sending this question.  While you may be interested in the amount of skin that can be removed its most important to ensure that the result is natural.   This procedure is irreversible and its safer to take less than more as secondary lip lift procedure can be done if not enough of a result is achieved.   The other limiting variable is gum show.  You do not want to remove excess skin and create a gummy smile. 

I think a 10-12mm philtrum would be short. I would aim for a length of closer to  14 mmm so around 7.5-8mm reduction at the most. Any more would make it difficult to inset in my experience. Always better to remove too little than too much - you cant replace what has been removed, but can always remove a bit more after a period of healing.

As a general rule the safe amount of skin removal for an aggressive subnasal lip lift is up to 1/3 of the vertical philtral length. In your case that would be 7.5mms. While 10mms can be done it is important to remember that this is an irreversible operation.