Advice on safety of cement block on fence

[dugit]

I have a fence at the back of the garden which is up on a bank. It consists of nine slotted concrete posts in) and the distance between each post is 6 feet. Also between the posts are cement blocks 17*8.5*8.5 inches . The present wooden fence panels which are slotted in between the concrete posts are 5ft in height by 6ft wide.
I was thinking of adding more cement blocks so that the wooden fence would be say only 3feet in height,is it ok to add further blocks from a safety point of view and if so could the blocks may be the full height of the fence ?(reason I keep losing panels in the strong winds/rain)