Here is my problem with that statement, which is typical of many I read: The 176 is the 5th of 6 lengths made for the MX78, according to their web site. The OP is 170 lbs and 5'8", which put him decently below average for both dimensions.
So if what LP is saying is true, then even average sized males should give up all hopes of skiing MX78's, because they'll be too short. And Kastle must be kinda bone-headed for producing a ski with such a narrow demographic target.
But I'll argue something else. (For the record, I'm 162 lbs, own several Kastles.) I think it requires LESS technical skill to ski a longer version of any given model, up to a point where you can't turn it. Length provides stability, which we all come to value partly because it's easier to have the ski absorb shocks (and compensate for our changes in CM from those shocks) than for us to do it ourselves. So what if we have become addicted to going as long as we can to compensate for other CM issues? (Anyone who can recall seeing Highway Star's old videos will know a nice example of this, but there are many others who prefer really long, almost always with the intimation that they're a stronger skier because of it. Or that it proves they're a stronger skier.)
Length, if you think about it, also means driving more static weight plus more swingweight at the tip. This means more muscular effort to initiate and hold a turn. It also means more force, at a constant speed, to flex the ski. That effort recruits more large muscle groups, particularly at the knees and hips. If you've ever switched from a longer to a shorter demo of the same ski, one run to the next, you know the outcome: You overturn the shorter version, with too much movement of the CM, because those big groups have become entrained to dominate the motion. Less weight and inertia allows proportionately more involvement of the small muscle groups chiefly used for balance. You become a "finesse" skier, whatever that means. (Sounds suspiciously feminine, huh guys? Bode rules for us!)
A level III I sometimes ski with prefers a 79 mm ski under 170 cm in heavy eastern chop and glop. In god's name, why? Because he says that it's more interesting, and gives him more options. In that stuff at speed on shorter narrower skis, you need to have your parts together, as they say in ballet, and you have to react very quickly to the constant changes. (In the east, that includes sudden exposures of ice or rocks under the glop, not to mention bumps that are very differently shaped than it looks like on the surface.) Not relaxing, perhaps, on a shorter ski. But is it a bad thing? Is a longer ski the "correct" length for him because he's an 180-something expert? (Don't worry, BushPA, he also owns fats, and longer skis too.) I'd argue instead that a shorter ski promotes a different style, wherein you are more likely to react, with more muscles, less likely to ride the radius, run over changes in terrain.
Recall reading here that a while back, member of the Japanese SL team at the end of practice was observed skiing the rest of the mountain at speeds over 60 mph. On a FIS-spec SL ski. I've seen club and master's racers manage that at about 10 mph slower in my local mountain all the time. Without breaking a sweat. Again, the big difference is that you have less margin for error in where your CM is. Gotta pay attention.
So I'm not necessarily knocking longer lengths. Unlike my Level III guy, and more like Bush, I'd want to go as longer if I were teaching all day, or if I were in no fall zones where stability mattered a lot more than perfect form. Or if your CM couldn't be perfect unless you were an alternative to the national team (trees, for example). But I am arguing that it doesn't follow we should go as long as possible everywhere just because we can make the skis turn.
Some of this is getting fooled by design, I think. Modern skis like Kastles are weirdly easy to initiate because of the dual radius and cutout or fluid tips or semi caps, or whatever you want to call the various brands' tips. So that leads many of us (myself included) to conclude that such skis should be skied even longer. (Will forgo the usual referent to claims of other long things.)
But what if those easy initiations are fooling us into going longer than is necessary or even good for our skiing? I bring this up in part because several respected members of Epic have argued that a strong skier in the 150-170 range will be happy on the shortest 2010 MX98 made (not necessarily true for 2011 because of massive changes to design, but you get the point). I skied the MX98 in a 184, middle length, and while I loved its (that word again) stability, and while it was plenty easy to initiate, even if bumps, by the end of the day I was beat up from the stiffness and weight associated with the other 3/4 of the ski. And I was not skiing as well as I should have been. I own the MX88 in a 178 (3rd of 4 lengths), and although it's definitely a more forgiving ski than the 98, and I love it just as is, in truth the length has limited my options. It's a great western ski in 178. In the east, it feels and handles big (probably because of the lower speeds I face on smaller slopes), and I move to other skis. I have a feeling that I could have purchased the 168, paid attention to my mechanics, and ended up using it more. Just a thought.
OK, you'll reply, but that just shows you're not good enough for a longer length. (This is a variant on the well known mantra that beginners and intermediates should be on shorter lengths because they go slower and need more help turning.) Well, no doubt I'm not good enough for a bunch of things. But logically, I can't find that the less proficient skier=shorter length conclusion follows for better skiers. The premises behind the first conclusion evaporate for better skiers. Your next possible reply is that unless you thrive on a longer ski, you actually aren't as good as you think. Ah, but that's circular. It can be dismissed unless you're into logical fallacies.
So I can't find a convincing argument that longer lengths=better skier, either as cause or effect. Lots of arguments for longer lengths=heavier skier. Or longer lengths=faster skier. (And obviously, correlation between faster and better, but correlation is not causality.) Technically better? Convince me. If you can.