I'm doing quadrilateral limb lengthening soon and I need your advice.

I'm 1.66m and I've saved up for what seems like a million years to have enough money to finally undergo quadrilateral limb lengthening to add 13cm to my height. Right now, I've booked my initial surgery and starting July I'll have about a 13 month time frame to attain my 179cm height. My question is how I should go about doing this. I've heard that doing the 2 lengthening processes back-to-back could decrease the amount by which I'll be able to lengthen.

What's most important for me is the absolute certainty that I'll get to 179cm in the end. After spending all this money on these 2 surgeries I really won't have the funds for additional lengthening if this doesn't work out initially. How much difference does the time in-between the two lengthenings really make? I don't care about the pain during.

What would my chances be of success if I were to lengthen 5cm on the tibias, then wait a month, and then do 8cm on the femurs?