I have a new question though for anyone who could answer.

Does the slots that the rivet goes into be a perfectly smooth? Because when we removed the old rivets we ended up creating a cavity of sorts inside a couple of the rivet slots. So, does the slot in the mud ring that the rivet goes into have to be perfectly clean and smooth?

I know if it is not the greatest of descriptions and if you need me to try and explain again I will.

We always rapped the rivets once or twice on the way to the hole to knock the scale off.