I hear you. Everyone must make their own risk assessments, especially when we modify gear.Thanks for the thorough explanation. if I recall, you actually remove the belt that goes around front? If so, there is no way I would feel comfortable in the saddle without a full and strong wrap around me that is buckled, similar to a climbing harness. Maybe it is just as safe, but I won't ever try it.
I might clip a little bungee to the lineman's loops on the way in in addition to the hard belt, but that's it.
My bungee mod does remove the belt, so if anyone doesn't feel safe with that, then don't do it. But the utilibridge used double duty as the bridge and the belt is essentially the same concept in regards to not having a true belt wrapping around the from of you at all times.
I do believe that the bungee belt will keep the sling snug on me at all times, so in the event of a fall (I'm hoping) the sling will stay tight enough to stay in place.
Think about it... Whether you are using the lineman belt, or hanging from the tether/bridge, the sling is pulled tight so I can't envision actually falling out of it. Is it possible that it could slide up to my armpits during a fall? IDK, I haven't tested that.
But crap happens, so only do what you are comfortable with the safety of your mods and climbing.