Thanks for your comprehensive response.
I've measured the current bolts I've used and they are 7mm from the bottom on the integrated washer to the top of the nut. This cases the dust caps to sit nearly 2mm too far out and they are not flush like they're supposed to be. This is why I thought there was a specific Campag bolt.
Now, what is the combined measurement of the Campag nut and washer that you have?
And would the Royce bolts fit flush in a record pista crank?