I have a saying about High End Tuning: "Everything changes Everything ELSE!" There are SO many variables to play with/ get confused with. So, after that teaser, let's talk about individualized tuning.
A good carpenter measures twice and cuts once, right? Most good artists and musicians have some idea what they want to create before they start. High end tuning is the same. You must have a goal in mind, an idea of what is standing between you and that goal, and an idea of where you are, and an idea of where your goal is- otherwise, you are shooting in the dark. AND you must work extremely precisely- as imprecision will spoil a tune.
So individualized tuning typically starts with video, coach feedback, and/or timing. As skiers get to a higher and higher level, they generally begin to know what certain tuning settings feel like and will be able to provide feedback directly- (USSA Phase 4 and 5 athletes).
So, if you want to help your athlete bump to the next level, ask their coach for some feedback on their equipment setup. Not all coaches are comfortable in this area. Some coaches are experts in technique and tactics but don't consider themselves geeky enough to dive into hardware questions. THAT IS NOT A NEGATIVE- We all have our areas of expertise, nobody can know everything. If you don't get an answer you are comfortable with, take some video to another coach that you know and see what they have to say.
Individualized tuning MAY involve changing base and or side edge bevels, changing edge finish, changing base structure/finish, binding mount, lifters, or even plate tuning.
I am sure I have raised more questions than I have given answers... BUT THAT IS MY POINT!! DO NOT just jump into individualized tuning without a plan or direction.
But WITH a plan and a decent level of skill, all KINDS of performance improvements are possible. And once optimized, the ski setup becomes nearly magical. Faster, smoother, more powerful etc.