The dactyl case has a 1/4" opening for a TRRS jack. That isn't big enough for any sort of 7-conductor jack, so I had to improvise.
My first idea was to omit the jack entirely and solder the cable in place. That wasn't satisfactory—it would have left me without a strain relief on the cable, and any damage to the cable would require a soldering iron to fix.
This was my second attempt: an RJ45 plug coming out of the case. The "boot" on the plug fit tightly into the hole for the TRRS jack and could act as a strain relief. It looked fine in my head, but once I had it in front of me I thought it was pretty ugly, and I wasn't satisfied with its reliability.