T113649 didn't quite go to plan so let's try this again. Someone other than Jon should do this.
Various static pages have been generated here: https://phabricator.wikimedia.org/P2172 - 1 which is the normal article, 1 with only the lead section - for the following pages:
These pages should be hosted on labs in a mediawiki like environment, where first byte is consistent in all the results, and visiting the pages should not generate any 404s and the JS should load successfully (note in the pages on Jon's site there are various 404 errors)
Test the performance lead section vs full article (ignore no images view since this can be done relatively easily on production) and report back your findings.
Sync up with @peter so we can make this activity as easy as possible going forward