I've read this:
That led me to this:
and per the end of #1, I installed this:
With the plugin I can see and test the rule I added via add_rewrite_rule. However, when I try the same URL request on the front end site I get a 404. I'm struggling to sort out why the rule isn't being applied.
p.s. Sorry about the links not being links but my rep from StackOverFlow doesn't seem to carry over to wp.SE