Tom, the ISC Swivel... That connection that is on the spine, It looks like a sewn captive eye.. Is that the end of your lanyard just attached to stow?
I think that the Shunt makes the perfect lanyard adjuster. You can use two separate ropes, even with different colors if thats your thing. I tried it with two ropes but quickly found that having a bunch of swinging ends just got tiresome. The u-loop or whatnot seems like it would be a hassle but it really isnt. Plus it allows you to have 2 6' lanyards which is what I really use the most, but when I need an 8' or a 12' I can easily shorten one to make the other the length I need.
If I need something longer than 11' or 12', which is rare I just use my climbline.
You can see in the picture I use a twist-shackle for attachment. I recently replaced that with one of those nylon deals, like a quickdraw from rock climbing:
https://www.treestuff.com/store/catalog.asp?category_id=223&item=1509 and I did not like that one bit. It put the adjuster way out in front of me and made it twist up and ultimately the cam didn't grab as hard and slipped, plus it got tangled with my ropebridge and climbline and basically it didn't work at all. A biner and a quick link did the same thing. So back to the twist shackle, which works fine.
Basically thats my only disappointment, sometimes I wish I could detach it and hook it up to my bridge or the rings on the bridge so I could suspend under a branch from the seat part of the harness as opposed to the dee's.
What I do in that case is this; I pull slack so the lanyard is as long as I need then clove hitch a biner and clip to the middle hole of the HC pulley, wrap the lanyard around the branch and then clip the snap to the biner. It isn't easily adjustable like that but I have only had to do that once or twice I think and it lets me sit suspended under branches to thin to limbwalk out onto for pruning.
Other than that I really like it and one of the guys on my crew put the same system together and he loves it as well. I have used Blaze, Sterling HTP, and old rock ropes. 11mm definitely works the best IMO.
Let me know if you try it out though.