I've been mooring at Cooper Island since the 90's. It is always "shifty" there as the wind curls over the top of the hill and swirls around the mooring field.
I hate it when the boat runs over the mooring ball and it bangs against the inside hull (catamaran) all night long.
But, the snorkeling there is usually good and it's a good hopping off spot to head to The Dogs, or Baths or even Leverick.

So, I run the mooring pennant almost to the starboard cleat, tied with a short line. On the port side of the boat I run a line from the cleat directly to the eye on the ball itself. This - at least - stops any banging in the middle of the night against the sides of the hull under the cat - and it leaves us on 2 separate lines. Hard to explain, but the boat has much less unusual motion...