It depends on what you actually mean when you say "sweet spot" - is it easier turning, more forgiving in fore/aft balance, lateral balance? Flex, length, shape and width all contibute to these factors. In order to isolate the affect of each, we must assume that every other factor remains the same. If every other factor remains the same, the shorter the skis are, the easier they are to turn. Also, the shorter the skis are, the less forgiving they are as to fore/aft balance. So there are trade offs, these being just a few. However, you would not be wise to make assumptions about the charactaristics of a ski based solely on length. I demoed an Atomic shorty slalom in 160 cm which felt like a tank. I also skied the K2 Escape 5500 in 174, and it was very lively andeasy to turn. So you will know about the ski and length only when you ski it, unless you want to take someone else's word for it.