To my utter astonishment the rivet casting experiment has been a complete success!
I poured the moulding compound onto a few test rows of rivet transfers a couple of weeks ago fully expecting them to be pealed off from the styrene when I attempted to remove the set silicone.
I was wrong. They stayed stuck fast, from which I tentatively conclude that treating them generously with decal fix, followed by a coat of clear varnish, may be the solution to my concerns.
Flushed with success I have decided that I am going to try applying these rivets to the masters for my forthcoming NGY ballast wagon and B wagon kits which should enhance them even further.
Lets hope this test piece was not a fluke and it will work just as well on proper masters.