Can't get Bullet Constraints to work

Hi I have some difficulties with the Bullet Constraints Tools addon.
I have Cell fractured an brick and let it fall on a frame (like a picture frame). Now I wan’t to use Bullet Constraints to make the pieces stick together so only get the pieces in the middle fall apart (since the most pressure lies on them) but can’t achieve that. No matter what I try every piece just fall apart with no force keeping them togther.
These are my bullet constraints settings:

and here is my blend. Fracture.blend (1.91 MB)

I have tried for varius models but it’s always the same: no force keeping the pieces together

Please help! Anyone?

Never mind