Since my caster adjustment was maxed out, I decided to modify the radius arms. I cut a wedge out with a bandsaw, stuck them in the press to bend the bottom plate, welded them back together and added a fishplate on top. That added about 4 degrees of caster.
Previously, I hadlowered the front ride height about 5/8", which would have given me approximately 1 degree of caster--moving from 3.5* to 4.5*, which completely took care of the little bit of twitchy steering it had on the highway. With this change to the radius arms, I added another degree, so I should be pretty close to 5.5* now, AND the adjustment is right in the middle of its range, so i can now add or subtract caster easily. I can also bring the front ride height back up if I care to, without compromising road manners.
In this pic, the caster angle is the same as before, when the bolt hole was all the way at the top of the slot.
The added caster made it even more rock-solid on the highway, although it does seem to want to pull right or left due to road crown a little bit more than it did before. Not necessarily in a bad way, just a change.
I originally planned on adding a swaybar to the front, but haven't taken the time to figure out how to fit one. I have nearly 4000 miles of living with it as is now, and I don't feel any need to add one. I think the natural radius arm binding, combined with the wider spring/shock spacing on the axle makes it nice and stable even without the swaybar.