reallyhardtofind don't mind being bagged, but at least get me on a topic I know nothing about. 

I will respond though as my right of reply seeing you have bagged me.

From my read of your vent, IMO your understanding of Aust Post policy is incorrect. 

IMO there is nothing in the terms and conditions of extra cover to prevent your buyer from putting in an extra cover claim to Aust Post as I outlined earlier. 

Whilst AP do not offer a fragile service, they do provide guidelines for packing more fragile goods. This includes that all packed articles must be able to withstand a drop of approximately 1 metre to prevent potential damage or breakage.

If the goods were packed in accordance with those instructions, and this can be demonstrated through the buyer taking the complete packaging that goods were sent in to post office, IMO there should be nothing preventing a buyer from completing a claim form - except ill informed AP workers.

So I will not apologise for my earlier advice, as others may read this thread and get an incorrect understanding based on your vent.