Can anyone explain why this "knee trick" works?
Just a wild ass guess, but if your riding with your legs tucked in against the side of the bike the cross wind pressure has a nice relative smooth surface to blow against producing quite a bit of force in the process. That is to say, all of the square inches of area of the tank, your leg, the tool boxes, fenders (mud guards) can receive the total force of the wind.
If your leg is hanging out into the airstream it creates a turbulence which breaks up the constant side blast so areas of the motorcycle like the rear of the tank, the tool box cover and rear fender that were getting the full side blast are no longer getting it.
Anyway, What did I do today?
I rode the 220 miles from Flagstaff, Arizona back to my home in Phoenix.
I didn't ride the shorter 'superslab' I-17 which is really boring even if it is 80 miles less distance.
Those 140 miles on I-17 are posted with speed limits of 75 mph so you know everyone else is going at least 85 with some up in the 90's.
Instead I rode the State Route 89 from Flagstaff past Lake Mary and Mormon lake to Clint's Well and then route 87 down thru Strawberry, Pine, Payson to Fountain Hills.
Beautiful ride between Payson and Flag' thru thick Pondorosa Pine forests.
The high temperatures in Flagstaff got up into the 50's (F) with lows around 20 (F).
Some stretches of road between Flagstaff and Payson still have snow along both sides but the air temperature was in the mid 40's (F).
From Payson the ride rapidly drops down into the grasslands and then to the Sonora Desert where the temperatures were in the high 70's and low 80's.
Good riding weather.
The G5 didn't miss a beat during the entire trip getting about 76 mpg.