Hmm, I would suggest you lengthen your knees... yup, definitely knees!
No, for real. Your proportions are really good. But I would say your Femurs because
a)Femurs are meant to be a bit longer than Tibias
b)Femurs because you'll recover faster (given you only do 5-6cm and not go beyond)
c)External Tibias are painful. Internal Tibias might result in some permanent knee pain.