Replying to How to stifffen ski boots?

note: when i talk about stifness i mean i stiffer flex.

So how do you make a ski boot stiffer? This is something ive been searching the internet for answers for but cant find any. I have SPKs so how would a shop stiffen them? Pros and cons of this? Ive heard it can harm the structural integrity of the boot... is this true? To what extent is that risk related to how well it is done? Is it permanent or is there a way to change between flexes? How much money would this "precedure" cost?

This is not something im intending to do in near future but possibly in distant future. Really im just interested in it. I like knowing my options.

(I know in ft's you can just change out the tounges)

Sorry for any spelling mistakes.