An uncommon, but very serious skiing problem is with skiers who have major leg length differences. Typically, these issues were caused by a serious injury (often either a car or motorcycle accident) and come with related issues such as fused ankle joints and severe leg misalignment. Because of this, we do not simply add a lift, but work through the leg length issue as part of the alignment.
In general, we usually consider leg length differences over 1/2" (13mm) to be on the extreme side. Whereas differences less than 1/2" are generally far less difficult to address and can be handled with stock industry parts, larger differences usually require custom fabricating a whole new sole for the boot of the shorter leg. From there, canting issues must be carefully addressed, and very likely a number of other alignment issues. Note that the amount of correction is rarely at 100% of the leg length difference, but somewhere between 50 to 80%. Most people we see with such issues have their shoes adjusted for height, and these are typically helpful in determining at what height the skier is most comfortable. Also, while shims can sometimes be used inside a boot for extra height, this method can cause other issues and is generally only good for small adjustments.
We have had a great deal of success with such work, and many of our clients have described the improvement as "incredible" and "life changing." The only negative, is this work is extremely time consuming and expensive. Jobs often take more than 40 man hours! Because of this, we recommend if you are in need of such work, please call us well ahead of needing the work. We generally do not have enough time to do the full job during the season. There are also a number of other concerns as to which boots will work with such modifications. Still, we love helping skiers with these issue, and look forward to seeing how we can help you.