Totally TRUE that a custom mold prevents that matchstick receiver from poking the ear canal, but alas! I have found that the older I get, the more my ear canals swell up (and go down) throughout the day. I wake up, and can not jackhammer a pair of hard-case custom molds in my ear canals! I have to be up and about for a couple hours before they seat correctly (so there’s lots of “WOOOoo_WOoOoOO!” going on with feedback).
The one thing that steered me to RIE aids is that a soft dome conforms kinda, sorta to my swollen ear canals, enabling me to put them in right when I wake up every morning. In my dreams, someone would come out with a custom case that is sort of flexible like maybe high-temp silicone? I’m clearly dreaming here …