I did research the bolt sizes earlier on. Most came in at 8mm. Some were 6mm.
Example of those similar to the set up I am using:
https://www.thefrenchbedcompany.co.u...-pk-4-uk-post/
https://zipboltonline.com.au/cabinet...mm-x-90mm.html
https://www.fishpond.com.au/Homeware.../9999098001649
This was an article which I consulted along the way. Not an insert connection, but again 8mm/5/16” bolt …
https://www.scottjordan.com/informat...queen-size-bed
A corner block is another way of avoiding any possible wracking:
I am tempted at present to just let the build proceed as is, and deal with any issues if they arise in the future.
Regards from Perth
Derek