Re: How to remove Marshall rivets?
I take it they're ribbed (whether for her pleasure or not) and not threaded/spiraly?
The channel would indicate threaded, where the channel collects whatever material is scraped away by the screwing-in action.
However, the pic looks like it's merely ribbed, which makes no sense as the first rib is going to ream out the hole to the point that the 2nd one and beyond will do nothing.
However, if you do get them out, it'd be a fine opportunity to replace them with threaded inserts. That would make future replacement of the corner caps easier. Probably eliminate the need to fill the holes, as well.