Fence & privacy options

Hi!

I have a slatted fence around my garden (new build) and at the end I want to create more privacy and use the height to create a wall of planters.

The neighbours side has a retaining wall (you can see the top on my picture) of about 6’ then the 6’ fence on top.  Posts run all the way down the wall on the neighbours side and are cemented into the ground.

I was thinking of either moving all the slate up and closing the gap or nailing new slate over the gaps.

However, we frequently get high winds as we are on top of a hill and I’m worried it will just create a large sail to catch the wind.  The fence also runs along the back of three properties (neighbours either side) and the neighbour behind so if damaged it would potentially disrupt 4 houses!

I’ve looked at bamboo screening but I don’t like the look and I’m not sure I’d be able to attach my planter!

Any ideas???