I've tried the assoc. diff screw and it definitly is better but I managed to break 2 of them over time. I didn't hit anything they just snapped with use.
They always break at the end of the thread leaving just enough thread sticking out of the nut so that I could remove it. I'm now trying a Kyosho screw, nut, thrust balls and washers. So far so good. It's 2.5 mm and should do the job.