Rear-end shimmy, panhard bars?

[jup06]

My 2015 Reg cab/6.5' bed bounces alot more than my 2008 reg cab/8' bed. I attribute the bounce to the shorter wheelbase and the stiff suspension. But I also notice a shimmy in the rear when hitting a bump while slightly turning.

 

I don't think a sway bar would do much for me in this case since the truck corners well but is there a way to cut that rear end left-right wiggle? Do they even make panhard bars for these trucks?