turn on the option to send the beacon
Hah! It turns out that "duration" includes blocking time - so it is NOT an accurate measure of the DOWNLOAD time for a resource. I added "download" as a capture of the actual download time - it is the sum of dns + tcp + ttfb + content. (Note that tcp INCLUDES ssl so we do not need to include "ssl" in this sum.) Base the "slowest" resource on download time (instead of duration).