I would go so far as to say that if constant good seal is not there, the measured FR is pretty irrelevant to that user as that wont be what they are getting. And if they arent comfortable for the user's use case it doesnt matter how good the seal is or the FR as they wont want to wear them. Only after both of those factors are sorted is it even worth worrying about the impact of the tips on the FR. I suppose absent of a personal measuring rig, everyone should try and get comfort and seal with the stock tips used to measure (at least the same material and nozzle size if not flange size).
The thing is that I believe that I get a good seal, because the bass is very strong (too much for me), but I still have weird issues with these IEMs.
I have been experimenting with the ∆ 10dB and the JM-1 targets and the congestion and muddiness/veilness go away. They improve the soundstage a fair amount and the sound is no longer as distant, but the harshness while listening to metal is still as bad, or even worse.
Preamp: -2.3 dB
Filter 1: ON PK Fc 20 Hz Gain -1.6 dB Q 1.400
Filter 2: ON PK Fc 31 Hz Gain 0.6 dB Q 1.300
Filter 3: ON PK Fc 33 Hz Gain -6.4 dB Q 0.500
Filter 4: ON PK Fc 37 Hz Gain 0.5 dB Q 2.000
Filter 5: ON PK Fc 470 Hz Gain 2.5 dB Q 0.700
Filter 6: ON PK Fc 1400 Hz Gain -1.2 dB Q 1.200
Filter 7: ON PK Fc 2900 Hz Gain 2.1 dB Q 2.000
Filter 8: ON PK Fc 6000 Hz Gain 3.2 dB Q 2.000
Filter 9: ON PK Fc 8200 Hz Gain -7.5 dB Q 2.000
Filter 10: ON PK Fc 10000 Hz Gain 6.8 dB Q 2.000
Filter 11: ON PK Fc 12000 Hz Gain -3.1 dB Q 2.000
At any rate, I still prefer this profile over their custom one.
This is how many user profiles I have tried (I also tried every single one that was included at the app):
It can be seen how hard I tried to make them work. And this doesn't even count how many differest tips I have used.