Now I can't quite follow this and I'm not the angler to give it creedence, the 4-5" section wasn't really about anti-eject, was it? Sean Meeghan who first put it in his excellent articles a few years ago here may be able to comment? I'm sure he won't have been the first to use it, but it gets a good explanation which is one I kind of agree with. I'm going for Barbel on Saturday for the first time in a year, I'll see how I perform and on what hooklength!!
Paul, I think (and I've used it) that the rig described is a perfect tangle rig (that's tangle not anti-tangle) , unless you pull a PVA stick through it or you're using a light weight hookbait such as maggots.
All that happens when it's out of the water, is with the slightest jolt it bounces the bait around or if you're overhead casting the bait spin around the hook; both causing tangles.
IMO Jim would be better off fishing as he was but with better balance. As his original set up literally was completely lacking in balance.
Starting at the business end; 10lb Drennan Double Strength snaps bang on 10lb and has very poor shock resistance properties. Subsequently it snaps very much lower than its stated bs.
Then 12lb Daiwa Sensor mainline, though it's not a low stretch line, to get any amount of stretch will require a fair amount of pressure. So the job of countering the surges from the fish are left to his rod, so he'll need a rod with an action like a fly rod or finally, a very lightly set clutch, which isn't the way to go.
So how best to improve things, the easiest way is to change the hooklength line (as asked), as I said in an earlier post: Ultima Power Steel, Ultima Power Carp or Daiwa Infinity, all in either 8 or 10lb. Though I think this will cost him bites but reduced losses, so probably the way to go.
Ideally though I'd suggest considering a different mainline, even if only dropping it down to 10lb or even 8lb but the OP stated he didn't wish to change.