Well, Zach at Universal air mentioned concerns about that. He mentioned to push on the side of the frame to see lateral movement but it doesn't move. I can contact air bag it to see what they suggest since that's where I bought the kit.
Pan hard bar would push the truck one direction when lowered?
Watts bar keeps it straight all times?
When you're cornering hard you'll have several hundred pounds of force (or more) trying to shove the frame sideways in relation to the axle. I don't know how big a boy you are, but unless you're secretly Jason Momoa, I doubt you'll get much deflection.
A panhard bar will cause the axle to travel sideways slightly when the suspension is loaded or unloaded, but the further the panhard bar mounts are apart, the less deflection. My Mustang came from the factory with a panhard, and I don't notice the deflection when autocrossing it. You'd have to be a pro driver to notice, and even then it doesn't hurt handling, you just have to account for it.
Watts links do not cause as much deflection; they actually cause the axle to travel in a very slight figure 8 as it cycles up and down. I believe they can cause some binding if they don't align with the roll center, and that will exhibit itself as snap oversteer in hard cornering. They're heavier and more complicated than a panhard bar.
Flipping that arm around to work as a 4-link might be the best bet, ala the '70s A-body coil suspensions. I'd widen the reach on those arms out into a V instead of a Y. The further apart the mounting ends, the better it will stabilize the rearend. Tuning the length of the arms and their mounting points will affect your pinion angle and anti-squat.