hold fixing in scan chains

Hello,

In  the design I'm working on I have lot of small hold violations (~30ps) in the scan chains. The design is small, and the FFs in the scan chains are placed very close together. So the data path is very small and so the hold violations. 

Techno used is TSMC28nm (hold uncertainty is 50ps)

In have about 500 FFs and about 1000 hold buffers are added to fix these hold violations. I had a look to the library to see if there is a FF with a smaller hold time or  a big CKtoQ that could help but there is no.

The 1000 hold buffers added increase a lot the area of my design.

I tried to use the "useful skew" feature from EDI but the problem is that "useful skew" can be used only to fix setup violations from what I understood in the doc.

Do you have an idea on how to control the tool to force it using "useful skew" for hold fixing.

Do you have any other idea that could help?

Thanks in advance for your help.

Best regards

Chris