I used to keep a flat ski when terrain got uneven, that was my panic/survival mode, it seemed like the safest and most stable position to be in....wrong. In actuality all that does it let your skis bounce all over the place, get deflected, and require mogul-master knees and Herculean strength to absorb the undulations and the rapid slowing and speeding up that occurs on this type of snow.
When skiing with Bob Idid as he did, and what he did was spend most of the time on his edges especially as the terrain got sloppier. The ski edges cut through all the little bumps and drifts of snow, rendering the ride almost as smooth as a groomer. I have been doing that ever since and I am dramatically better at handling uneven terrain, in fact it no longer phases me, I rip on eveything (but moguls....I'm working on that). Coupled with my new wide, slop skis, I can hang.
Thanks Bob and ESA