Thanks for your insights and sharing your experience. I have no direct experience with Sundown or Fi drivers, only going by specs and what I have learned in phone calls or emails, as well as the experiences people like you share.
I'm not about to buy either to test right now, I've got lots of more important things to drop coin on than drivers that are a maybe...
Now - to throw my own experience in the ring....
As far as I know, the CVX has next to no inductance mitigation in the motor. No Cu, no Al, nothing that I am aware of. Even so, and running it with coils in series, I achieve decent matches with the CVX. Not saying that inductance doesn't matter, just wondering why it isn't an issue with the CVX.
Here is the LilWrecker as measured vs the HornResp model (and the Hornresp model is an approximation, lacking one flare).
Other than it being a bit cool out when we measured, I don't think the match is all that bad.
SPL is within a dB, low corner is within a Hz, and it matches the impedance measurement as far as the tune.