Been way too busy moving stuff into storage the last week, the workbench is still a complete mess but hopefully it will be useable again soon.
I've got at least one starter here that someone has fitted a solid rivet too, of course this would be fine if it was one of the earliest engines.
I also have a couple of NOS rivets too, not tried fitting one yet either, but I did fit a pop-rivet to one a few years before I got the NOS ones, luckily the steel insert came out leaving the hole for oiling.
You could do with finding someone that does "EDM drilling" to add a hole to that rivet that just spins when you try drilling it.
David