I know this is not the standard opinion here but you can do more research on scientific sources to check alternative opinions. You should also simulate lenghtening in a mock picture. In the first decades of CLL you allmost allways did tibias only.
If talking about proportions, never do 8 cm alone in femurs! If doing one segment only, do 7 cm on tibias (or even 7,5/8 cm if it's a good, experienced surgeon, and if things are going on ok during the process).
In this case, doing tibias alone has also other advantages altough it may take a little longer.
Femurs are already the longest bones. If additionally lenghtened, you will have your knees visually too much "pushed" to the ground. It will look weird specially when leg nked like on shorts, in the beach, with your partner, etc.
On the other hand, aproaching tibias measure to femurs usually doesn't seem awkward. This may be due to several reasons, one of which is that the shorter you are, the shortest the tibias usually are, also in relative terms.
I would avoid surgery in two segments for safety reasons (and to avoid enlarging that diference to wingspan altough this is less relevant; see below).
But if you really want more than 7,5 on tibias only, do 5 cm more on femurs. [You can do more on femurs but I would stay on the saffer side, specially if tibias are extended those 7,5 cm, to avoid disruption of "entire leg" biomechanics. And also because femur lenghtening is very "heavy" for a big mass of soft tissue and muscle. You have a lot more physiotherapy "education" to do on your body, like glutes that become weak and make it hard to seat for example.]
DON'T THINK ABOUT ARM LENGHTENING!. You will have another relatively risky surgery and enter into a SPIRAL of disproportion: hands too "short" for longer arms, torso too short also, etc.
Also, there is no such thing as a perfect wingspan ratio. Our bodies are not governed by any "golden number" taken from Ancient Greece or Da Vinci. Except extreme or special cases, like some sports, dance, etc., for ordinary observers, nobody notices or cares about wingspan/ leg ratio in daily life.
