I think you've changed the topic after I answered.
Let me answer your second question according to my opinion as well.
"Would doing 4cm on femurs or tibiae result in a better recovery?"
We cannot guarantee that, so i'm not going to answer this question. But you need to know that you tend to have less complications if you don't go past 5cm.
That's being said, let me talk about the segments.
"I meant I am only going to do 4cm on EITHER femurs or tibiae but I'm not sure which. I had originally decided on tibiae as I always felt like they looked short. But I guess the most important thing to me is which would lead to a better final recovery."
Well, proportionally; PROBABLY 4cm on tibias will look better and make you look like TALLER from a far distance.
But, tibia is always riskier than femur and femur is recommended 2x than tibia.
There are a lot of things we need to pay attention to.
Like, consider that your inital femur was 40cm, and tibia was 37cm.
If you lengthen your tibias for 4, your tibia will be LONGER THAN your femurs. This is literally against the laws of nature and human body. Your femur has to be longer for a better agility.
Another thing: What do you except?
Do you want to guarantee your athletic abilities? Well, we cannot guarantee that but I can totally say that if you go for femurs, you'll more likely to reach the point you always wished to reach after LL (athletically)
Tibias are always harder and riskier as I've mentioned before. If you don't care about it and your proportions allow going for tibias, do it.
Best Regards