Yes turn them so they look like diamonds, and yes always have the grain run at right angles . I have never used the fiber tape.

Turn them 45 degrees (to the crack) like a diamond?  I have read where others indicate that the grain of the wood in the cleat needs to be 90 degrees to the grain of the wood in the crack so that the crack will not pull apart again in the future.  Also some folks have advocated the use of a fiber tape running along the crack between the cleats if the crack is a long one like this one is.    

Ed , not a particularly hsrd repair,I have done many of thin type on violins. Treble side cracks are common.  I glue the seam and pull it together with clamps, I then make square spruce cleats turning them so the points if the cleat runs with the crack seam. I would place them about every inch or two.  If your real careful pulling the crack together you dont even need to refinsh any of the top.  Kevin. ...