maybe naive but how can you tell whether you are under or overgeared flex-wise? I definitely can turn but some skis are easier than others to bend and drive. how do you know when you have the "goldilocks" level for you?
Too short is an easy one. You know when you have a stacked washer-dryer and the washer is on spin cycle and the entire thing shakes and sounds like it's about to blast off into space? It's the same sensation on skis. You feel fine with the terrain and could bomb it comfortably, but you have to make turns just to keep the speed lower to avoid the spin cycle sensation.
In a more technical sense, when you bend a ski, you apply energy (force) to it. More advanced skis handle the energy in 2 ways - either being stiff enough that the ski doesn't overbend, or bending a lot and snapping back - being "poppy" - returning the energy so to speak. For the wood in your skis has a modulus of rupture and a modulus of elasticity that captures stiff & poppy qualities, and the same concept applies to things that stiffen it, like fiberglass, titanal, carbon stringers, etc. If your skis lack the elasticity and the stiffness to handle your force, you could theoretically break them, but thanks to a bunch of physics that's *way* over my head about how we turn, they generally just wash out instead.
The question of how long is too long is a little trickier. You should be able to steer it. That changes a lot depending on where you are on the mountain. I'm on a pair of 162s. On the toughest run at my local hill, I wish they were 3-4cm shorter. On most off piste terrain, I wish they were 3-4cm longer. On groomers, I'd love to add 10-14cm. Since I spend 80% of time off piste, I'm making due for now and demoing things in the higher 160s for when I "grow" into them, hopefully as they go on sale in the spring. If your E84s ride like a quiet Cadillac on the groomers, it might be worth trying a shorter demo to test out on steeper terrain. If you dabble on tougher runs, I wouldn't build your setup around the shorter length.
As for handling your nervous sweat at the top of intimidating runs, ski it, then ski it again, then ski it one more time. For my first day skiing doubles, only 1 run had decent snow conditions and I ended up lapping it around 10 times. Surprisingly, you do get a slight boost in confidence when you stand at the top of the run for the second time and think to yourself "I skied this. And even though I fell down 14 times, I didn't die, so there's that."
Oh - and in terms of your E84s vs your friend's skinny skis, the skinny ones sound like carving skis. Those are easier to get on edge since they're specifically built for it. Width is part of the reason the 84s would be harder to get on edge, but a true carving ski has a ton of torsional stability as well. If the 84s were just like a carver but with a wider platform, they wouldn't be nearly as forgiving for an intermediate skier and would lose any ability to float in anything more than a dusting. In terms of whether or not you should dedicate time to carving technique? I know I'm beating a dead horse, but it depends what you're hoping to learn. There are several ways to make a turn - carving, skid/steering, jump turns - being good at all of them would make you a very, very good skier. I've personally worked on steering most. It gives more options for turn shape and speed control. My goals were to get down hard things, so steering was great for that. I've only been exploring carving as I feel comfortable on the entire mountain. Those turns generate a lot less friction, which means more speed. You don't necessarily have to learn one then the other like I did. You could perfect your carving on all the runs you're confident on now first and then up your terrain game, or work on both throughout each ski day. Do you need a carving ski? On one hand, they're built to be the best match for carving turns as you learn the technique. On the other hand, if you're looking to use carving skills all over the mountain and not just perfect corduroy, you'll be carving on something else at some point. I don't think there's a right answer.
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