Can I pull this off?

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Do you think I can pull off 5cm, possibly 7cm?

Age: 19
Height: 173CM
Wingspan: 177CM
Arm Length: 68CM (From fingertip to inside of armpit)

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Would you say my tibias look proportionate to my femurs at 7CM, or is that too much? I've roughly measured my tibias at 37CM, and femurs at 42. Though that might not be completely accurate.

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Oh crap. I think I didn't do this properly.  I've attached another image, which I think is a geniune 5+CM (in tibs).
I'm new to this, so bear with me.

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Actually, I think I didn't mess it up before. Here's a comparison with my original height. It looks more like a 4 inch difference, doesn't it? No wonder my legs look so long!

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Hope it isn't too much to ask, but could someone make me some mock ups for +5cm and +7cm in tibs? I really can't seem to get the measurements right. 

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Thanks, think I've worked it out now.