Ski Diva Extraordinaire
If someone has a limited or an excessive ankle ROM you put them in a stiffer boot.Oh, this echoes my experience. I am a pretty conservative skier, I do not necessarily like to go "fast", but rather it depends on the outlay of the slope and the turn I am trying to make. I am definitely more of a finesse skier. However, I am hyperflexible (double jointed) and my bootfitter told me for my ROM, a higher flex was the way to go. I'm in a 115, though he did warn me that flex was not the same across manufacturers, even boots styles from the same manufacturer. I was in a very low flex 80 boot before and it was definitely too soft.
If you have limited, then you need the stiffer boot to access the pressure you put into the ski with the limited ROM.
If you have excessive ROM, then you need the boot to "push back" so you can flex the ski.
If you're normal ROM, then any flex could work depending on your personal skiing style, etc.