How to show HTTP POST Request parameters (through Inspect) on a popup window

I wanted to see what HTTP POST request parameters were being sent using the "Inspect" feature in Firefox.  The page was a popup, and when I clicked on "Inspect" and reloaded this page, a different page appeared.  I solved it by temporarily opening all new links in the same window.  You can open the Inspect frame, go to the Network tab, and then click on the link that will open the new window.  This blog says to do this in about:config:

browser.link.open_newwindow => 1
browser.link.open_newwindow.restriction => 0
browser.link.open_newwindow.override.external => 3

Ironically, I'm opening the above link in a new window. :)  So test it out.