Only time I have push troubles on and off trhottle is when I use 35mm rear foams. I use 30mm foams front and rear all the time.
I just thought I'd add the springs deal if all mentioned failed.
Your lucky with the thrust brgs. But.. I also have a neo saber 1/8 car, ( serpent clone) and never have had a thrust brg failure. I agree with alot of maintance on the brg, greasing and little to no endplay . After using the centax theres nothing else like them, you can keep 2 and 3 shoe clutchs,on short or long tracks to me.