I owe many thanks to Sohron for his beautiful pictures* and detailed description and also Ashimoto who gave us pics that show how brackets can be checked for the correct shape. Helped me a lot. Glad to pass it on.
* Is it just me that now - thanks to Photobucket -has them blurred? Anyway, I've downloaded the Sohron CB550 Assembly Manual that shows them unblurred. So let me know.