There's the problem. It is true that modern skis do not track straight when completely flat, and that is initially disconcerting. It is also true that you get used to it surprisingly quickly. The usual fix is to always be on edge, at least a tiny bit. You can also ride a flat ski (for example for maximum glide on a flat run out) and get used to the way they feel. Tell yourself they feel "loose" instead of "squirrelly". If you have good edge awareness you will be fine. "Catching an edge" has largely disappeared as a fall cause.
Yeah we’ve definitely changed the way we ski in our relationship to a flat ski.
Definitely having to straight tuck on a 165cm/12m is pretty hairy. I’ve had to do it a few times for a long stretch, say 400m in Switzerland. A spot where you want to get a lot of speed to make the runout. It’s pretty damn squirrelly. You’ve got to just be real quiet and try not to move much, yet be supple. Of course I could just make big radius turns, but not as much fear/challenge involved,
The same run on the 180/21m would be no problem. Go longer and straighter and it’s nothing, a joke, everything's calm and easy and you just want more speed.
But straight runs can be pretty rare. Unless you really want them, then just get appropriate skis. On slalom skis I’m not looking for long cruisers to tuck. I think years ago on straight skis I was always looking for stuff to tuck.
OP, i can relate. Basically 20yrs ago, the year I bought my first shaped ski, I must of demoed a dozen pair. Everytime, at the end of the day I’d go to this one trail where you can see the whole run, and tuck it straight down the side near the woods. I didn’t want any damn shape ski that couldn’t go straight.
Towards what became the end of the demoing period, i rented the Volkl P30. The last generation. Wow, I really liked that ski. I tried it in the 193, then 198, then 193 again. (God, my body hurts just thinking of the longer one. It was work. Still, I was considering that length because you know, it’s still “short”, and skiing involves effort.)
The thing is, by the time I skied the P30 for the second time, I didn’t care about the straight run. Odd, but it was no longer important. I remember trying a couple others, and I’d make my mind up about the ski well before the end of the day. Going straight really wasn’t where the thrill was. Speed in a turn, the ability to actually carve a turn at normal speeds was where it’s at. Angular velocity and g forces are more fun with less risk.
Ultimately, if you want to really learn the technique, it’s best to get on a carving ski that’s narrow, <80mm, 165-170 cm It’s just easier to learn in a smaller space at normal speeds.