Hey man thanks. Damn I wish I had gotten a copy of my new lat ceph. The wilckodontics surgery I had in May has decreased my mentolabial fold significantly. Before this, my lower lip almost touched my chin, but now you can actually see the whole fold whereas before it was so deep it was completely hidden.
Because of this I believe that sliding genioplasty will look much better. I will try to get the new ceph from my orthodontist this week to post it here, and I will also post pictures of my profile too. Your help will be appriciated!
Is double saw surgery off the table? Because while I agree a genio with vertical lengthening done correctly should soften your mental-labial fold while also adding projection... your fold is still pretty severe. I worry it may not be sufficient or end up looking how you want. That's still a decent deep bite you have with a flat occlusal plane and jaw recession. All of which can be completely corrected via upper and lower jaw surgery (Probably clockwise rotation, down grafting of your upper jaw and then a mandibular advancement).
Ultimately any procedure other than jaw surgery will be just be masking the issue (but still potentially giving a good result) but I understand why you would opt not to have a such major surgery and all the crap and unpredictability that comes with it.
Now as far as choosing a surgeon... I would not choose (unless I had too) a doc if they don't already have experience with this kind of aesthetic oriented surgery in addition to focusing on function. And from your consult, it doesn't sound like they do even if they are a competent and skilled surgeon. Have they at least done a genio w/vertical lengthening before?
And is going to an out of state to find doc a possibility? One that specializes and has a lot of experience with chin surgery. I'm just thinking of the best route for you but I also understand the cost and logistics of going to a far away doc is not possible for some people.
And finally to answer your question, the picture you put about 6-7 mm of movement for both dimensions is a good guess. Usually 8mm is the maximum before you may see a step-off.
And although it's not universal, the 1:2(or 2.2) for ideal upper lip/chin ratio is a good guide to use. So if your upper lip is 22 mm, your chin length (from the superior tip of your upper lip to the bottom of your chin) should be around 44-48 mm. Still, your chin could be just as long now or longer so the ratio may not be helpful.
I wonder if the lengthening should exceed the advancement... So maybe 7-8mm horizontal and 5 mm vertical?
Oh and I just saw you that mentioned have a more recent ceph? So your mental-labial fold is reduced compared to the pic in your first post?