I am doing 6.5cm on tibia.
I would be happy doing that. however the plan is to do 5cm femur after the 6.5cm tibia (surgery 5 months apart, back to back.)
I know there is a lot of debate in this forum about proportions. When I first discovered this surgery, I just wanted to get tall without any regard to proportions. Then I got my x-rays and measured my tibia/femur length. I heard that the perfect ratio is 0.8 tibia/femur. Being within this ratio would probably give your legs very nice proportional aesthetic appearance, and at the same time better equilibrium while squatting down, walking up stairs, maybe even running.
In order to maintain close to this perfect ratio, I would have to get two separate lengthening surgeries. The way I determined how much to lengthen each segment was to do the following:
1. Determine goal height (eg 183cm/6ft)
2. Initial starting height (eg 170cm/5'7")
3. Determine original tibia length(eg 40cm) and original femur length(eg 51cm)
4. Your starting tibia/femur ratio is (40/51)=0.78 (slightly longer femurs than average)
5. You need to lengthen 13cm to go from 170cm to 183cm.
6. You add 13cm + 40cm(tibia) + 51cm(femur)= 104cm total final leg length.
7. Your new femur goal length is going to be 104cm/1.8= 57.78cm
8. Your new tibia goal length is going to be 104cm-57.78cm= 46.22cm
9. So now you have 46.22cm(tibia) / 57.78cm(femur)= 0.79999 = 0.8 ratio
10. So to achieve this ratio from the previous starting bone length;
a. Tibia lengthening required is 46.22cm - 40cm = 6.22cm
b. Femur lengthening required is 57.78cm - 51cm = 6.78cm
I just thought I mentioned this since you are considering doing both segments and you can determine how much to lengthen down to the last millimeter to get very proportionate legs.
I watched Andrewshizzles first Youtube video where he is messing around in his bedroom, and you can notice that every time he squats down, his body weight forces him down on his ass and he makes it look as he is doing it on purpose. Having very disproportionate limbs will throw off the center of gravity and equilibrium beyond what your physiology will be able to compensate.
Just thought this might help just in case you didn't know this already.