Here are a few tips. Keep in mind that your mileage may vary. For example, perhaps you’re more susceptible to the occlusion effect (so you have to have larger vent diameter), or you have more sensitive skin in the bony part of the ear canal (however, as @Zebras mentioned at one time, it can be strengthened by proper getting used to).
Maybe a “0” length wire could be too short for you (for me, it is perfect), etc., etc.
Put finger in your entraces of ear canals and try to feel if movement of head of temporomandibular joint makes part of ear canal wider (rarely narrower).
If movement if quite large (few milimeters) - it’s worth to consider making silicone impression with open jaw (2.5 cm mouth opening) with bite block for the whole time since silicone injection to the end of its curation.
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