Unless there is something terribly off about my reading comprehesion, that isn't what he wrote. He said that weight and power were factors, not necessarily "more important".
Regardless of your video (which I can't see at work, and just injects too many irrelevant issues, including exactly how fast you ski, exactly how "less than optimal" conditions were, etc.), I don't agree with your surface area theory of ski stability even now that you've attempted to flesh it out.
I have an imperfect counter-example to your Top Fuel vs. im82 anecdote: I had a pair of 165cm Volkl 4-Stars a few years ago. They were significantly less stable than the 155cm Salmon Equipe 10 SC's that I had later, despite having more length and surface area. What this does show is that ski construction between different models is a significant factor, and you can't draw any conclusions if your points of comparisons were different models.
Those 4-stars were also wet noodles in torsion rigidity. Somewhere on the web (in this forum from years back, I think) is a photo of me twisting the 4-stars to 20-30 degrees of deflection with my bare hands. (I'll attempt to find it later.) In contrast, the Equipe 10 SC's were significanlty firmer in torsional rigidity. This is in-line with skier219's point about the increased torsional rigidity of newer skis, and another reason why your Top Fuel vs. im82 anecdote doesn't work in a discussion about stability as a function of length.
Despite being in agreement with skier219's concept in overview, I actually believe the effect is more complicated (as he may, or not). It might be helpful to think of skis not as rigid levers, but rather internally-damped leaf springs. If you can visualize leaf springs of different lengths partially anchored with a significant mass at each end (one end would obviously represent the skier, the other being the forward point-of-contact of the effective edge), you might see what I mean. What is also a factor is how the manufacturer "scales up" each length to produce proportionally firmer skis. Regardless, the general rule is that keeping skier and model of ski constant, a longer ski will be more stable. (Of course, this is not saying that longer is necessarily better for said skier. That is another can of worms.)
Edit: Now as I think about this again, the skier, being also in contact with the surface at where he/she is in the middle of the ski, albeit not entirely anchored, same as the tip... the ski also acts as a traditional rod/mass damper a la archery. In this case, length (and mass) directly affects the damping of forces the main mass (skier) is subjected to.
Edited by DtEW - 4/3/2009 at 05:46 pm
Edited by DtEW - 4/3/2009 at 06:18 pm