Last fall I attended a clinic hosted by several PSIA examiners where we were videoed every day. A professional boot fitter was also in attendance.
After watching me ski and reviewing the video it was determined that although I stand bow legged I ski knock kneed! No-one had ever told me that before. The cause is my tibia is curved. This is apparently not that uncommon of a condition. One of the test was to glide on one ski on a gentile slope and look for a drift left or right but it was the video that confirmed the condition. The cure was cants, 1.5* on the left 1.0* on the right. The fitter used shims like the SVST shown above.
My boots had originally been fitted by a professional boot fitter who made custom insoles and I was also biostanced. These are all static procedures. It took the dynamic condition of skiing with a high level instructor and reviewing video with a boot fitter to devise a cure. I think it has help greatly.
One test you can do yourself is to glide down the fall line on a very gentile slope on one ski. If you drift to one side or the other you are pressuring that edge. You can then put 1/2" wide strips of duct tape on the boot sole typically the heel only like shown in your Stenmark example. A three layer strip of duct tape is about 1/2*, I wouldn't go more than 9 layers thick. You may have to try the canting on both the inside and outside of the heel to determine which provides a reduction in edge. For me, I was heavy on the inside edge, I would drift left while gliding on the right ski. But since I was skiing knock kneed the cant was applied to the inside edge of the boot to push my leg to the outside. If you are truly bow legged you should drift right when gliding on the right ski, heavy on the outside edge. Try the tape on the outside edge first. If your able to determine an improvement take that information to your boot fitter. It would also be good to have video of you making medium radius turns on a moderate groomed slope to give the fitter a good example of your dynamic stance.
I could also be very helpful to book an hour with a Level 3 instructor and get some input before visiting the boot fitter.