Hi @Philbo,
Welcome to the Bunnings Workshop community, it is wonderful to have you with us.
Unfortunately, with a shade sail of that size, it would be best to have an engineer assess the brick piers and suggest a suitable method of attachment, as when the wind gets under a shade sail, particularly one of a considerable size, the forces exerted on its attachment points can be far greater than most would anticipate.
While I could suggest some fairly robust attachment methods, I couldn't ensure the pillar would be capable of supporting the wind loads applied to it. For this reason, it would be best to speak to an engineer to ensure everything is done in a safe way.
Assuming the concrete pillar is deemed suitable, they might recommend something like a Chemset and anchor stud attachment system.
Let me know what you think, and if you have further questions, please don't hesitate to ask.
Jacob
