As we know the safest amount of lengthening from double LL is 8 cm from femurs and 5.5 cm from tibiae which makes a grand total of 13.5 cm height boost in legs (actually 13.3 cm due to femur curvature). It's a solid 5 inches of added height and 5 inches longer legs.

Assuming one is 5'5 at night, after 13.3 cm he will stand at 178 cm at his lowest which basically means standing at 6 ft with high quality elevator shoes at night.

IMO, getting solid 178 cm height from 165 cm is where double LL is worth the most as you're going from a very disadvantaged height to completely average and decent height.

This graph illustrates the point very clearly as to why you get the most ROI from double LL of 5 inches at 5'5 starting height:

https://ibb.co/p4vrshr

Starting from 5'10 most women view you as a man who has no height disadvantage and will not shove you off based on your height alone. Only minority of women might view you not tall enough and even then you can compensate with other things at that height and have decent chances with them nevertheless.

And this is what legit 13 cm height difference between two men looks like:

https://ibb.co/6wJ5MXc

As you can see on the photo above, it's a dramatic and life changing height difference. And the ROI is 1000 times higher getting that 5 inches of height at 5'5 in order to become 5'10 rather than get double LL at 5'10 in order to become 6'3.