Elevator shoes are a great way to imagine yourself after lengthening(mostly for tibias tho) . For example if you wear shoes that add 6cm,all you have to do is to inagine your leg going all the way down without the shoe.
A point to make here is that your muscle will look weird, something which isn't the case, since with lengthening it will also grow and won't look weird(after you build the muscle back because it will be atrophied for a bit)
Sadly tho its harder to do the same with femurs. For me personally 6-7cm looks fine and around 9 it begins to look off. But bear in mind that femurs are naturally the height bone. So it should be naturally longer than tibias. This applies not only for proportions but most importantly about long term knee and foot damage and/or arthritis.
