16 cm in one go is unreasonable since you can't lengthen your tibia for 8 cm and lengthening your femurs for more than 8 cm is also not recommended.
IMO, you should measure your bones with x-rays and lengthen according to initial bone length values. You shouldn't exceed 15% of original bone length. To be more on the safe side, 12.5% is what I think the upper max safe limit. This means that the shorter your starting height and bones, the less you can lengthen safely.
And it's not only about safety, it's about appearing normal after double LL. Nobody will look normal after 16 cm unless one starts at 185 cm height with huge torso and arms.
For guys below 5'7, the most realistic option is 5 or 6 cm on femurs and 4 or 5 cm on tibia for a grand total of 9-11 cm height increase. Of course with only sequential quadrilateral of at least 6 months gap after femur surgery. I don't recommend starting with tibia because it takes longer to recover and you won't be able to break your femurs after 6 months of tibia surgery.
I too would like to be 16 cm taller but it's an unrealistic and dangerous goal for so many reasons. Even if it was as safe as 5 cm femur + 4 cm tibia lenghtening, I'd still not lengthen that much due to biomechanics and proportions. I'm used to lower center of gravity so 5 cm on femur and 4 cm on tibia is already pushing it to adapt to new biomechanics and center of gravity.
And, finally, imagine 5'3 guy lengthening 16 cm and becoming 5'9 1/2. He will look very odd due to short torso and freakishly long legs. Even if he does AL, his forearm and hands will remain ridiculously small for someone standing at 176 cm tall.
Lengthen according to your initial bone lengths and don't exceed 12.5% if you want to remain functional and more or less acceptable proportionally. For me at strong 5'5, 12.5% of femur is about 5.5 cm and for tibia is 4.4 cm. I might even go lower and settle with 5 cm femur and 4 cm tibia, i.e. 11.5% original bone length.
If you're 160 cm, 4 inches is already pushing it. If one is 165 cm, again, 4 inches is already pushing it but at least he can get away with it if he has short legs. If one is 170 cm, he can get away with 10 cm if he has short legs relative to torso. And only after 173 cm can someone gain 13 cm safely and look normal if and only if he had really short legs relative to torso. 16 cm is only for dwarves IMO. Nobody should lengthen more than 11.5 cm or 4.5 inches in total and that's already pushing it.
Thx for your long reply! Yeah I think he does not do 16cm in only one go because that is indeed too insane... my tibias are 34 and my femurs are 40.5cm, but I measured with a tape. By the "formula", it seems to me 12cm or so is the upper max limit.
And yeah disproportionateness will also be a big problem even if I can accomplish 16cm.
My goal is actually to get myself taller to the degree that I can be treated normally, or at least my socializers will not define me by my height(I think as long as a man is averagely tall he will not be defined/judged by his height, and he should not feel inferior to tall guys since at that point everything comes before height, not like under 5'7 face personality etc. come after height... it's brutal to say but this is how society works).
The reason why I am considering doing it, even though I do not fall victim to blackpillisms like if you are short as a man your life is over(I think even a man is an amalgamation of height face personality IQ etc., and if one person defines you 100% by your height then he is not someone you should socialize with or care about. That's his problem after all), is that however I am in other things height comes before them, like 'This "short guy" is smart!", "This "short guy" is rich!", etc., namely height is too 'significant' out there, and I really hate this. I don't want to impress others by my shortness at all.
In China, 170cm-190cm is the range in which no matter how your height is people will not define you by your height. Nobody will mention your height when claiming something about you, but if you are not in this range then they will.
(I have to mention that, China is now the most heightpilled country... I am really wondering why. It seems to me for a man, even ugliness or poorness, particularly poorness is not discriminated so badly as shortness...)