So far, so good, regarding impedance. The other point one needs to look at is power handling, or rather, core losses per applied voltage.
With that core, and 12 turns, approximately 170V RMS, end-to end over the 12 turns, will cause a core loss of roughly 300mW per cubic cm, which given the core's size makes about 8W total core loss. Under continuous carrier conditions this would probably overheat the core, unless there is some forced convection, but under ICAS conditions it should be fine. Slightly lower voltage would be fine under continuous carrier conditions.
If that common mode choke is used in a 50? antenna system operating under textbook conditions, 170V end-to-end means 340V between conductors, and that would be about 2.3kW into a 50? load. So this CMC could actually be used at legal limit power. But if the conditions are not textbook-like or specially if the system impedance is higher, your mileage may vary.
These values are for 1.8MHz. On higher bands the core loss goes down.
Stacking two cores allows using 7 turns to get about the same total core loss. The inductance will be slightly more than half, so the impedance at the low spectrum end will be lower, but the stray capacitance will also be lower if the turns are kept optimally spaced, improving the performance on the high bands. At least so says the theory...
