Hmm, watching Joshua's run, right after the start, there is a period he is at 4500-6500 for a good 5-seconds, and varying in that range. Since peak torque is happening at 4500 (if I remember correctly), so maybe shifting at the start of that section, then only dropping out of it after the slalom could have give a few more mph in there without loosing much.
My attitude has been how long am I at redline in any given section, but maybe my attitude is how long am I over 4500RPM in any given section. Though in 3rd you would be well under 4500, so maybe its how long am I in the 5500+ range, and does that section facilitate going to 3rd?
This weekend I am headed down for an event at a go-kart track. They call it an enduro, as its 5 laps around the outside of the track, guessing those 5 laps is in the 2.5-3min range? That could allow a chance to hit some 3rd gear and keep it there...