I tried SingleFile briefly. It works. Looks like a well thought out and put together addon.

One thing I noticed, when you have the option enabled for "include the info bar in the saved page," the page actually shows a floating icon in the upper corner. If you click on this icon a flyout will indicate the time the page was saved, then if you hover over a tiny button on the flyout the original URL will popup. Clicking the tiny button takes you to the original URL.

This all looks nice, but I prefer the way Save Page WE does it. Save Page displays a fixed header bar with the full URL and time the page was saved. For someone like me who's always paying attention to the URL bar this is nicer. It's easier to understand that the page you're viewing is an archive, and easier to get to the original page with a single click.

Note that both the floating icon in SingleFile and the header bar in Save Page WE can be closed.

I also notice that neither SingleFile or Save Page WE works in FireFox reader view. A small thing, but it would be nice. That's what I was really looking for when I tried SingleFile.