I think you're obsessed at the moment (who'd guess in a CLL forum?) and may need to take a step back to think.
I'm thinking this mainly for two reasons:
1. You're obsessed with proportions when at such small lengthening amounts, no one will notice a thing. Some people have naturally longer tibias and shorter femurs than usual, and vice-versa.
2. I think you fell prey to the "6 feet mentality" in the US. Your aim with CLL is basically just to reach 6 feet while maintaining "natural" proportions. What worries me, though, is that let's say you had already gotten the two LLs and are now 184.5cm. Was 179cm your night height with bad posture? If it was your morning height with good posture, maybe you'd lose height over the day and get to 182.7cm at night. That's not 6 feet anymore. Maybe, then, you'd start worrying again and want a third CLL.
If you're really in a rush for CLL, external tibias seem the only option, but it takes very long (I remembered it takes a month to heal for each centimeter gained after your last thread). Otherwise, it'd be best to live at your current height and just save for more comfortable, hopefully full weight-bearing, internal femurs when you're older and with a high-paying career in medicine.