I run the tire untrued straight from the box to maximize the life of the tire (they are expensive). I never had any problems with chunking unless I have a huge crash.
I even ran some OOLLLDD Jaco foam tires which I think are at least 8 years old, the ones with smaller diameter grey rims and thick foams. I left them untrued and ran them as is and I still didnt have any problem with chunking.
I like keep my car's ride height at around 4-5mm since asphalt tracks arent as smooth as carpet and my chassis take a huge beating if I run the car too low. I run the tire till theres about 2-3mm of foam left before I throw them out.
I guess it also depends on what type of surface you run on. If its an parking lot track then that might have something to do with it. I run on dedicated asphalt rc track so the surface should be a lot more smoother.