Okay. I've posted a guide to equalizing headphones to match an ideal loudspeaker response.
If you have an "ideal" IEM, you can pretty much follow this guide, except using your reference IEM as your reference speakers.
If you can, follow the steps in that post up to step 9 and post a screenshot of the equalizer settings you've arrived at so far, then I can talk you through the rest of the process. (of transforming another pair of phones to sound 99% like the JH11 or *gasp* make another pair of phones or the JH11 themselves sound better than the JH11)
The remark about room nodes in step 9 doesn't apply to headphones, of course. OTOH, if you find sharp peaks and dips above 2kHz (probably much higher than 2kHz though, for in-ear customs), those may be ear canal resonances.
Well I don't actually own the JH11 or UM Miracle I can only demo them, but you're convinced I can change a basic IEM into 99% of their sound, is that correct?
I will have a look at your guide, and dedicate some time to see what you're getting at.