[CSX 4027]

Regardless of what you did with the rose joint position, you didn't really have to change it. It was probably OK even with all the threads on one side. If someone had set it up that way, there might have been a reason with the castor. It appears you might have another issue that could have been wearing the tire funny. The control arm bushings are probably worn and have movement yielding it next to impossible to control toe under acceleration and deceleration. This is a common problem easily cured with bronze bushings with zirk fittings. The Kirkhams can help you with that.
My original 4027 rear suspension was exactly like yours. The rose joint was also set up the same way with the threads. I also had the delron or urethane bushings that were junk. Everytime I was on the track the car was unpredictable until I changed to bronze. Then it became a predictable car that I could steer out of a corner on the gas and not have to check my underwear.
Put the rose joint back the way it was unless you know for sure it was even at one point and moved which I doubt and get bronze bushings. Also see what type of bushing is in the housing under the seat where the toe link connects. It should be steel.
The idea is you want the whole system solid or the toe adjustment will never help. When the car accelerates the rear wheels want to toe out. When braking, they want to toe in. Only way to stop it is make it solid./