We have had many successful doctors that perform cosmetic lengthening and will do it without a lengthening limit. Some of the best surgeons in Russia, Germany, and the USA have lengthened people 10 cm or more on a single segment - Dr Augustin Betz, Dr Ghassan Salameh, Dr Alexander Barinov, and Dr Shahab Mahboubian are a few examples. So where do these lengthening limits come from? Quite simply the less experienced doctors. The ones who have no clue how to handle a complication that comes from lengthening larger amounts are the ones who will tell you to stop at 5 or 6 cm. Because a few less experienced doctors in the cosmetic field such as Dr Donghoon Lee, Dr Mangal Parihar, Dr Brikholtz and such say to stop at 5 or 6 cm for lengthening it now has this forum acting like leg lengthening a worthwhile amount is akin to jumping off a high rise. The simple fact is you will come out close to 100% if you go to an experienced doctor and the ones who have the experience are the ones who have no problem letting you get your money's worth by lengthening a big amount at once. They actually have more ethics too despite what others say because the ones with low lengthening limits are the ones who will tell you to come back and operate on the other segment for more length, which will end up costing you double to four times the amount in the long run, whereas the doctors that will let you hit 10 cm on a single segment are letting you save money that way and do not care about lining their pockets.
Reconsider your fear of large lengthening amounts because the opinion of amateur surgeons does not hold water against the opinion of famous professionals.