this is my favourite topic , it is also very frustrating. i have seen some of the top doctors for chin wing in europe , and NOT ONE could show me a case where there was a dramatic improvement in width of the patients jaw, i.e. the transformational kind we are looking for and that are possible with implants. anecdotally i have heard about an austrian doctor that has widened by 10mm though.
i think there is a combo of reasons for this, mostly that there are not that many cases done where this is a priority. secondly, even by slicing the jaw up and filling up the gaps with your hip graft, you are simply not getting the incremental volume of material that you would need.