as I have always understood, Korg ceased supplying the cardboard spacers when the Kronos 2 was released back in 2015.
I've owned both vintage, and I'm wondering whether the metal "key slip" panel, (I'm a pianist)

I still ponder this, as I am still using my own cardboard wedged across the middle when carrying the board just in relocating locally. Because when I pick it up and the centre area rests against my stomach, there is still some give pushing toward the keybed, and to me, it feels about the same as the Kronos X 88 I used to own. There is a slight inward bend if I don't use the spacers.
I'd love to know whether Korg officially state that the metal keyslip panel is actually stronger than previous models or they've just reviewed there policy and just to be safe we should transport it with them anyway,
I'm eager for anyone else view on this.....