I sold off my old ice tools for newer ones. I got Petzl Quarks as I wanted a tool that had leashes but could go leashless and I found I enjoyed the swing better than other tools on the market that fit the bill. I had not climbed leashless, so I wanted to start on them with leashes. That idea didn't last as the first time I went out this season I kept the leashes in my pack. I found climbing without leashes to be such a release. Now ice climbing is more like rock climbing. I can shake out easily and placing screws is just as easy. Even yesterday while climbing it made some mixed type moves much easier to do where I used a branch as a hold on a climb. This is not easily doable with leashes if only for the mental concept of the tool being attached to you person.
So after my first true leashless experience back in November I knew I needed to make umbilicals for my tools in the event I do a multi pitch route with them. I started with the information on AAI's blog to make my own.
Their version calls for a swivel, which I don't feel I need. I am not doing anything fancy like switching and matching at this point to make that a needed part of the umbilical. Removing the swivel keeps weight and price down when making your own too, so that was also a concern of mine. Speaking of which, it was about five dollars for the 1/2" tubular webbing and 1/8" shock cord both in twelve foot lengths. Adding a swivel probably jacks the price up to $10. (Still much cheaper than a $45 one from Black Diamond.) I followed the instructions they had and used bailing wire to snake the shock cord through the webbing which made it easy.
However, the instructions that are provided incorporate the length of the swivel into the system. Upon completing mine I found it too short for the way I wished to use it. So I added a loop of webbing to extend it and hopefully use it to girth hitch to my harness. It turned out to be still a touch short, so I now clip my extension loop onto a biner on my harness. If you are planning on doing this yourself, test often. I think the only sure test before cutting is to try it on with a harness and take some swings. Make sure to take a few to the side as well. If you are tall like me and don't plan on adding the swivel, the full 12' would be a good starting point. Since I have Quarks, I made small loops of 4mm cord to clip climbing carabiners into to loops.
Having climbed on the umbilicals once, I can say most of the time I do not notice they are there. However, there were a few occasions where they hooked on screw heads or icicles. But I'd believe with practice that those events should diminish.