Originally Posted by Magnus_CA
You left out some key details...
What should the point of the plumb bob align with on your boot when you're in the stance?
If it's off then what adjustment should be made?
Sorry. As I do it, and I may be hilariously off on all this, these assumption: 1) In a skiing stance with the proper sole insert/orthotic, your foot is neutral (neither pronated nor supinated), 2) In this stance, since your CM is forward of your normal standing CM, it is distributed more toward the base of the first metatarsal/BOF, and 3) the midpoint of your patella should be at your BOF. Therefore, the tip of the bob should bisect the BOF line. Put in a less technical way, when you load your leg, your kneecap should always be over the middle of your foot just behind your toes. Works for all sports I know of.
That takes care of the longitudinal axis. If the bob tip is medially or laterally off from the bisect point, you have two options. The best is to get thee to a bootfitter and get a different insert, since odds are yours is still off. The quick and dirty solution is to adjust the cant of the boot with the handy allen wrench. But of course it's not a real sole cant but just an adjustment of the barrel of the boot as it sits on the body. This will help align your leg and patella relative to the boot body, but won't do much to help the distribution of force as you flex, since the tibia will still be misaligned relative to the foot, and it will tend to create interesting new pressures/hot spots on the ankle as the barrel takes some of the force each flex cycle.
Now if you have messed up knees that actually don't align with the tibia, or if you've got curved tibia, you're pretty much screwed in terms of simple solutions. Maybe a real medical knee brace, or a good fitter can do more nuanced stuff using an orthotic, or actually plane down the boot sole (which is what racers do). Do not try any of this this at home.
So that's my longwinded version. See, "bingo" was actually better.