I just did 8 cm femur and one guy did 7 cm tibia , we  had same day surgery ,
I am 9 weeks into consolidation , he is 4 weeks into consolidation .

we both  have very  straight legs , no complications  besides minor infection .

Tibia takes more time to lengthening ,   and more recovery time . more money too .

if you are only   doing one LL , you can get 8 cm on femur for MAX safe limit . 1 more cm is still 1 more cm .