Scott,

All very interesting.  At the time of intstallation I was ready to give
up 10 kts.  I figured I'd still be saving time over the belly wipe down
after every flight.  In the end my 10 mile post to post speed run had
less than a second difference in top speed (measured with the highly
suspect eyeball and stopwatch).

There's a lot to be said for some sort of lower cowl exit stiffener.
This is the 1st I've heard of such a device.  I have a blast shield of
sorts driving all hot air off the cylinder fins down and aft toward that
cowl exit.  It is my belief that I have very little eddy currents
running around my firewall.  And in fact I've had my last #8 screw pull
through on the right side of the cowl.  At the time I thought my Dad
just failed to remove the last screw when helping me drop the cowl.  It
may have been the high force of the exit air flow.  I added a tinnerman
as a temporary stop gap.  It has held for some 50+ hours.  

BTW, if you'd race with us at the Airventure Cup I'm sure you'd be in a
fine position to take a photo of that cowl exit bow.  One has to wonder
while people now have the ability to build pseudo constant speed
propellers that twist based on RPM if the lower cowl might be modulating
according to CHT limits.  Bring your telephoto lense :)

Larry Henney
N360LH