JC, I was taught to set the tweeter X-over at 1.5 to 2 times the Fs but as you said, JL doesn't publish that data (which I find strange).
I did read on JL's site for the C3-100ct (1" tweeter) under the "Overview" tab;
"Inline 12 dB / octave high-pass filters with tweeter protectors are included with this kit. The C3-100ct is designed to operate above 4 kHz with a minimum high-pass slope of 12 dB / octave."
So what I did is send JL tech a question if they could provide the Fs (no was the answer) but below was also JL tech's reply; (which is why I set the x-overs where I did)
Hello, for the C3 speakers I would suggest a high pass no lower than 4,000 Hz at 24 db slope for the C3-100 tweeter.
Then bandpass the midrangefrom 4,000 Hz down to 80 Hz.
For the passive speakers I would high pass them at80 Hz at 24 db slope. Then low pass subs at 80 hz at 24 db slope. I hope thishelps.