Exclide did 7,5 on his femur with an exfix, so I am not too worried since I'd only do half. I also think that Dr. Solomin and Dr. Kulesh are way better than Dr. Sarin.
If it turns out it's risky I'll do tibias though, I won't risk my health for 4cms of height.
Dr. Solomin said external femoral lengthening can be discussed after some x-rays are done to evalute the risks.
p.s. They do have experience in LON\LATN for femurs, they wouldn't offer it otherwise. The reply to my question was, that it's just very painful and that it's recommended to stay below 5cm per segment.