As you know, tibia LL won't change the perspective of how far down your arms reach relative to your thighs, but femur LL do. Since tibia LL is safe up to 2 inches and most of us want more than that, we have to keep in mind that before lengthening our femur, there's a limit of how acceptable looking we end up and it varies to person to person (depends on starting proportions).

Now, armspan to height ratio is still changed with tibia lengthening and we won't be able to reach our toes the same way we can before tibia LL, the same goes for femur LL. But, visually, where arms rest relative to thighs is more important to avoid that T-Rex factor.

IMO, hands should reach at list mid thigh (femur bone length divided by 2) to look acceptable. If the ratio becomes less than 0.5 it will progressively start to look off and T-Rex effect will be created inevitably.

IMO, the best way to get the idea of how far down your hands go relative to your femur bone is to get a standing X-Ray where you relax your shoulders and arms in parallel to femur. When they measure your femur bone length, you also draw the line besides your middle finger next to your thigh to know how far down it reaches quantitatively.

For example, if someone's femur is 40 cm long and his hands reach below 23 cm from upper end of femur, it means that he can get away with having 46 cm femur length and look normal. That's because his hands in theory could reach below 20 cm from upper end of femur and look normal at his original height.

You have to understand that when you lengthen your femurs for 8 cm with PRECICE nail, your hands go up to 4 cm higher relative to your mid-thigh post-lengthening. You have to keep in mind this ratio where your hands reach relative to your thighs to get an idea of how much can you lengthen your femurs without looking suspicious.

If someone's arms reach about 55% lower from upper end of femur bone and his femur is at least 44 cm (typical for 165-167 cm guys), it means that he can get away with 4.4 cm of femoral lengthening and end up having his hands exactly at the middle of his thighs.

It's a very useful ratio to evaluate before lengthening IMO.