I agree with those who say don't help Parker on his defensive mismatches against guys like Barnes - at least not on a consistent basis. He wasn't doing that bad a job anyway, I think, trying to be physical with those bigger dudes.
Also, don't collapse too much in the paint when players like Jack penetrate. I'd rather have him take a contested midrange shot than have guys like Curry or Thompson wide open on the perimeter draining threes.
I also still think going big with Duncan/Splitter is worth a try. That way, the Spurs could pack the paint more and still have their perimeter defenders stay close(r) to the Warriors outside threats.