Rittersport and myself have both. Others may too.

Tkfc hits harder compared to DX12 with the extra headweight and its fairly easy power, where you may have to hold back a bit at times (with clear mainly or lifts the odd time).

The stiffness is quite similar, but i find the tkfc very marginally easier to use, as the headweight gives assistance to shots. The tkfc has a slimmer shaft too.

Tkfc is slower in defense. When practice swinging (and in real use), it swings a decent amount slower. I haven't been able to fully test speed and ease of defense yet.

Control is very good and much better than tkf Ultra that has the 5.8mm shaft as well. I find the DX12 has amazing control, so tkfc would be one step behind that. Ive liked the feel and control on all aerogel rackets I've tried so far.

Last comment is i feel hitting with the tkfc feels more dampened and im not sure if its due to the frame differences or different strings. I'll know after changing strings.

Let us know how you go