Someone said it above. . . take out the spring, and bottom out the frame. Then set it up so that the bar is like and 1/8 of an inch away from the rear while bottomed out (stick a piece of cardboard in there). Put the springs back in and see what it looks like. You can also make that spacer from the bracket to the rod end a bit longer. It's just some tubing and a bolt. . . if that works, I'd weld a little gusset in there just to add some strength.
What's funny about this store bought panhard bar bracket at the diff end, is that I made an attempt at mimicking with my ideas. With it installed with my homemade ladder bars built to fit four bar/coilover brackets, my car felt like it wanted to bobble at most any road irregularity, and especially bridge approaches or exits that are more uneven. It may be because my ladder bars mount lower to the axle housing compared to P&J's setup. I went from an 18" panhard to a 32" panhard and made an incredible improvement in rear suspension induced car ill handling. I've questioned how much the altitude position of the V to rearend housing affects suspension action if the ladder bars pinch together at the front like P&J builds their product. I'm on coilover rear shocks vs. transverse leaf setup. PM me if you have insight. A longer panhard bar is better, and a bar set parallel to the axle is best.