I am a Cped on the medical side of the fence. I have a fair amount of boot fitting experience, albeit several years ago. Earlier this year I visited a shop that caters to the local junior race community. The shop uses the Sidas HD Vac system and Sidas blanks. The owner told me they no longer post footbeds, instead they punch for ankle, navicular, 1st, or lateral 5th; whatever is needed. He told me that this is the method taught by Sidas. While shopping with a friend looking for new boots, we visited a shop that also uses the Sidas system. I was told the exact same information.
I was taught that in stance phase sports, the heel,1st and 5th need to be on the same plane. The posting material used to achieve this plane was based on the weight of the person and the mobility of the foot (firmer for heavier/mobile, softer for lighter/rigid). If the foot isn't supported properly, unwanted frontal and transverse plane motions are introduced. Punches are a function of volume; a punch done on a boot without properly supporting the foot is equivalent to trying to hit a moving target. That being said, there have been many so advances is ski technique and boot and ski technology I fear the methods I learned may be falling by the wayside.
The intention of my inquiry is to learn and grow, not to bash or get into an argument about methodology. I respect the experience and advise offered on this forum. I was hoping one of you could enlighten me.