NYSkier, being a bit old school, I've been slow to embrace the short ski revolution. I had the chance earlier this season to demo the same 172s (only size available), but bypassed thinking they were too short. After further education, much of it from this site, I decided they might be worth trying after all. They definitely didn't have the rock solid stability of the 177 AC4s, but given their lively performance, I didn't even tend to push them in the speed limit department. I was too busy making effortless turns!
All I can say is for my weight, stability at speed never felt like an issue.