small number of timing failures

de-em, on your original question:

1) When the design fails a little bit on setup, it really can't do much more. It has basically placed to the point where it doesn't see any moves that would help timing. The only thing that would help is by ripping up tons of logic and starting over(which may help and may hurt). Basically it is running a different seed. So for setup, the answer is no.

2) For hold, it should be able to do this. Note that hold timing is met in the router by adding delay(the place won't ever place things further apart). First make sure Assignments -> Settings -> Fitter -> Optimize Hold Timing is set to All Paths and the Optimize Mulit-Corner option is checked. Without these, the router won't try to optimize these paths and it will naturally fail. These used to not be on by default but should but are now.