Sensible answer
The book (para 0218) says the buckles are to be on the left hip of the wearer. Pretty clear I thought. There is no mention of the silver bit.
Also, an exciting bit of news is that a new style, similar to that worn by RAF regt will be available soon. It has the bird (have never seen a definitive answer about the species) on the central portion and 'Royal Air Force' on the circular hasp. Presumably this will make it easy for the wearer to put it on correctly.