[dsraven]

if you can make the panhard bar almost as wide as the inside of the frame, keep the frame mount low so the bar is level at ride height, and hide it directly behind the axle, then the geometry is good for the bar so the axle movement side to side is minimal with suspension travel and also it isn't too much in the way for routing other stuff like exhaust. bear in mind that the level bar will mean the axle will always move side to side in one direction, towards the frame mount end of the bar, because the arc that the axle end of the bar moves through will be at it's furthest away point from the frame mount end. short panhard bars will mean the axle moves side to side more as suspension travels simply because the shorter bar moves through a shorter arc. for air ride trucks that want to be in the weeds but raise to drive around this will mean the tires may need more clearance between the fender. when mocking up it is always good to run the suspension through a complete cycle from lowest to highest with the correct tire and wheel in place as well as the body, just to make sure it's all good.
thats just my 2 cents, others do things differently.