Tight or solid bushings in mounting locations that are not "wallered out" will go a long way also...When I put enough air in my bag to really help cover up those other little details it would lose some traction consistency.
I didn't have many issues until the transbrake went in the car and 60' times got into the 1.4x's
I also use a cargo coil in the passenger rear and a broke down stock spring in the driver side, the bag is just riding these days.
Not sure how much power you are putting to it and how you're launching it. ?
It has NOTHING to do with any actual "frame flex", it's the nature of a coil sprung, 4 arm system to do that, and all the action like that initiates at the rear mounting arms, bushings, and locations, I mention that because front suspension, motor plates, mid-mounts, etc., etc, will do nothing for your problem.
I went from this.....
To this....
Back to this only by fixing the rear mount holes that were wallowed out.
