Don't know if this will help ,but here goes.
Skied ( mostly watched ) yesterday with two skiers ( both 6', one 160, other 200 +)swapping back and forth an Atomic 9.12 (160). Steep bumpy hardpack top half, wide open smooth hard bottom. They ripped this ski like nothing I've seen.Very,very good experts. Super quick turning on the top and amazing carves on the bottom. Impressive!!
Asked them their opinion ( I'm interested in short slalom ). Both, need to be edged. Stability (160lb) not an issue. 200+lb said was not as stable and thought the 170 would solve that problem.