Glenn, how tall and what's your weight? ?Just how fast do you ski?
gary is like 5' 8" and 155ish, so a cheater SL ski (this is not a bad thing) like a 165 SS is perfect for a carver ski. I am 6' 170 (now) and I ski on 170's front side and my Watea94s are 178's. ?Stability? My "fast" skiing is some where around 40 mph, It's pretty fast but no where near many others, I have not seen a stability issue with my Dynastar LTD's (172), Supershapes (170) and wateas 84's (176).
I have to agree that a good centered stance is paramount. Lenght becomes more of an issue at high speeds (real fast skiersm, not hackers like me)in powder, crud and heavy stuff for improved fore/aft and float. The other factor to always consider is the running lenght of the ski. Twin tips, take 8mm off the lenght, turned up tail, 2-4mm. If you are in doubt, take a flat-tail ski, place it on a flat floor, take the ski you are not sure of, line the two points of each tip where the ski starts to make contact with the floor, then go look at the tail, see where the two tails make contact. You can get a quick idea of just how much less running surface there is on the turned or twin-tip. You may be very surprised. So when you hear of guys skiing a 192 Watea101, keep in mind its really about a 183-185 ski.
try this out on your own skis, you may be surprised by the differences even in a 170 vs. 175 ski.