I went out to the hangar to work on Shane's intercom. Getting there before him, I plugged my headsets in and they worked just fine. When he got there, we plugged his headsets in and they squealed. We went through the dip switches on the headsets, setting them to stereo and changing the mic gain to match mine, and everything worked fine.
After testing everything worked, we installed the jacks into the tub and one ear piece stopped working. We futzed about for a while and bent the jack slightly to make connection, then everything worked again and we could zip it all up. A final test showed everything on the gyro working as expected, so we went home to install the headsets into the helmets.
We got part of the way through, only to find I didn't have the tiny Torx bit we needed, so we went over to Shane's and rounded the tip off of his T6 bit. We figured it wasn't going to be easy to refit the headsets to the headbands anyway (there are parts you have to cut out,) so we broke them apart and fitted them to the helmets. Now we just need an aircraft to test them, and then test the whole setup in the air.