Personally I haven't had much benefit with drafting in my HCH.
Not sure if it is the shape, me or a both.
As I've mentioned before I live in a very hilly part of the country so I haven't had any long flat areas to judge by....mainly on hills and short flats.

I've not been closer than about 50 feet behind a truck except once and watched to see if I could squeeze at least 4MPG better than what I was previously doing.

Sometimes its the same but with a small margin of gain it's hard to tell.
I've been in the HARD turbulence, one time got ahead of it but very dangerous with no reaction time so I backed out.
90% of the trucks whiz by at least 5-15MPH faster than my given speed and in those cases I don't want to waste the fuel to catch up.
A couple of times I have matched their speed but it was hard to tell the benefit.

I've noticed several tiny pits in the paint on the front of my car. Not sure if it's caused by the few times I've gotten behind a truck.
I'm personally really paranoid if I get too close that fate will have the truck pick up and toss some metal junk. This happened to my Caravan in a rainstorm, and I have a half dollar size puncture-like dent followed by a 9" scrape on the hood and a nasty windshield pit / crack to show.

New sweet spot discovery:

This may be old news to some of you, but I just discovered it Friday nite.

In my MT 2004 HCH, in 5th gear, 34 miles per hour on a flat road, with a warm engine, my realtime mpg meter hovers between 80 and 120 MPG.

I don't know why, but slower than 34 and faster than 34 does not give the same result.
I used it Sat and today to bring my current tank up to 52.6 and I now look for places I can go 34 miles per hour!!

Hi Lars-ss:

___First off, your HCH’s CVT is probably locked up with no change in load at its highest gear ratio and you have the most minimal amount of friction from the ICE all the way to the wheels on the ground. Remember that Krousdb’s Prius II record run came at or around the low to mid-30 mph speed as well. The following should help explain the ever larger increases in power needed to overcome simple mechanical friction as RPM’s increase …

http://www.ornl.gov/~webworks/cppr/y2001/rpt/121813.pdf

___The Insight 5-speed’s FE peaks at or around 32 - 34 mph also. Just a touch above lugging in 5th gear and she will average 120 - 130 mpg all day long in warmer temps and no wind … With wind, then you are speaking of some real wild averages ;-)

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net

Thanks for that info Wayne....I have the manual tranny, so I have a little more control on where the RPMs go at each speed....

Hi Lars-ss:

___Sorry I missed the MT part above ;)

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net