Should I order a hard or soft custom mold?

I have an open fit RIC. I’m right between sizes in the open domes. The smaller size slips out, even with sports locks. The larger size are a little uncomfortable, but stay in place with some occlusion of lower frequencies.

So, I have a dumb question… If I go to a custom mold, does that mean total occlusion of lower frequencies, which, of course, defeats the purpose of open fit?

BTW, I have hard acrylic custom earphones made by Ultimate Ears. I’ve had them for years and they are amazingly comfortable, even with extended 12-14 flights. I still use them with an EQ app on my iPod when I travel. Properly fitted, they are no issue. I use them when I run and they don’t budge. I wouldn’t hesitate to get hard molds.

You could get an acrylic micro-mould sleeve made with either a conventional vent through it or a v-notch in the top or bottom to prevent occlusion. Lots of configurations are possible. I usually request a 2.4mm vent (moderate LF loss) and bore it out if it isn’t enough or add a sleeve insert if it’s too much.