I have a '17 T/A, 5.7/6-speed with the Super Track Pack, launch control, and other nonsense. You can launch it at 2500 on the street and it goes pretty well, chirps the tires through the first few gears, spins slightly at launch with the traction control off.
I took it to the local 1/8th mile a few weeks ago for shits and giggles. Despite the owner having the balls to call this place "the house of hook", the car SPUN LIKE MAD. The first pass, the launch control didn't activate, and I launched it around 4k. It wheel hopped at the launch and then unloaded the tires every time I shifted. Ran 9.8 at 81. Launching it at 2500 with thew launch control, it didn't hop, but still spun, and unloaded the tires at every shift. I eventually got the car to run 9.15 at 83, 2500 launch, shifting at 5500, no traction control.
That being said...I would not even begin to consider racing this car regularly unless I put a solid axle in it. The IRS is awesome, the car drives amazing, but scared the [censored] out of me at the track (I've been 8.70's in an Omni chassis car, FWIW). There was another guy running a new Scat Pack with Drag Radial's that day at the track...he was hopping worse than myself. I'm not real "up" in the new Challenger world...but I'm sure they have some sort of modifications for the IRS set-up. From what I have read though...people are claiming these cars are fine in stock form at the dragstrip. Supposedly better than the Mustang/Camaro. I would think someone makes a better than stock bushing to replace the OEM pieces in the rear. I think any type of regular abuse would call for such.
My personal opinion is that the launch RPM is key. I think if you could wire a two-step up to the clutch pedal to launch the car at 2-3k RPM's, you would be much further ahead as opposed to throwing money at the rear end seeking a miracle cure. Like I said about my car...at 2500 it launched smooth, at 4000...hopped like mad.
