Congratulation on a fantastic accomplishment.
You, Brett, Jeff, Michael, Aaron, Al, John, Sue and all the other JMT record seekers have taken this to an entire new level from the time I first "thru-hiked" the JMT in 1996 hauling a 75-85 lb pack and "Waffle Stomper" boots.
By 2003-2004, thanks to the "UL Revolution", I had my pack
weight down to 22 lb and thought I was as light as possible for a multi day trek in the Sierra.
However, as I said, you guys and Sue have taken this to an entire new level and I can't congratulate each and everyone of you enough.
Say Ian,....7.6 - 13.6 mph is a awfully fast start pace.
In a way, "FAST PACKING" (Speed Hiking) is a lot like
"SEX"......"Once bitten, forever hooked" and like in sex
a fast pace is important, but what is more important is how long you can keep it up.
Next time, whatever you are doing, try a little slower pace, but keep it up longer.