I'll half-disagree with the assertion that using a rear only is a massive increase in oversteer, at least with the bars from Hellwig for the Broncos.
I'm sure it was increased, and in the theory of things you're absolutely correct that this is what happens. But in reality, at least for one that I know, the difference wasn't a negative. Adding one of the new Hellwig anti-swaybars to the rear only (as an experiment before installing the front) resulted in very good handling on a buddy's Bronco.
This was on a '67 (now owned by 904Bronco here in fact) that was used as a daily driver and the guy was very happy with the results. Even happier when the front got installed, but with the rear only it was not at the dangerous range at all, at least with his driving conditions.
And he's an experienced driver. His daily driver when I met him was a very customized Shelby clone '66 Mustang with many ongoing suspension mods. Since then he's had trucks, cars, vans and whatnot as daily drivers, and was happy with the way the Bronco handled.
Perhaps it would have been different if he'd had to experience an emergency maneuver? Very possible, and that's where more oversteer would not be good. But as an around-town kind of thing, it had great road manners with just the rear bar installed.
I can see the light rear weight thing as well, but it's also taller in the rear, with weight higher up. Which I would guess has an effect on roll.
Perhaps this has a positive effect by not letting the bar induce as much oversteer.
And speaking of the front, the new aftermarket ones are not mounted to the radius arms like the factory and some old aftermarket ones were, so would appear to be more effective. They seem to make a very noticeable improvement as well, according to customer reports from those using just the front only.
Unfortunately, no detailed reports decoding oversteer, understeer, or specific characteristics. Usually it's just a "hey, this thing corners so much better!" kind of report.
Paul